Well I just finished a little trip up and down the road to test the electric fans in the 85 degree heat and calculate gas milage for a little up coming road trip.
This trip was about 16% stop and go city driving and 84% interstate driving with speeds around 55 to 60 most of the time, all most no drafting.
I neted just over 31mpg for the hole trip, milage was calucated useing yahoo maps and the fuel sales slip.
I also had a little vegetable oil and +6 points worth cetane from the Power Service in there too.
The electric fan (still only have 1 of 3 wired up) only came on once near the end of the return trip. The high flow thermostat, huge radiator and a little air flow are enough to cool these trucks when not loaded.
Also I had water only as coolant and for some reason the cooling system wouldn't pressurize again. I have a new 0.7bar (9.8psi)radiator cap that came with the radiator I am going to stick on there. My 16lb cap must have a crack in the rubber gasket or some thing because this is the third little trip in a row that the cooling system didn't pressurize.

nice to hear. what sort of milage you figure you were getting before the fans?

I could get around 27 not drafting doing about 55 to 60. But it was kind of rare for me to drive 55mph by my self.
Besides that I have logged thousands of miles getting about 25mpg doing about 65.
Driving 80 to 85 mph gets me about 18mpg, speed kills fuel economy on these trucks.
I guess when diesel was $0.70/gal there was no point, so what it got over 20mpg good enough back then I guess.
Now diesel is over $4/gal and I want all the fuel economy I can get.

80-85mph OMG!!! i've never gone over 70 in my 6.2's and that was only to pass!!!

also, your mileage is awesome! I average around 20mpg in the colorado mtns. maybe i should look into intalling some cooling fans when i put my new rad in!!

What rpm are you turning at 55-60 mph? I am trying to get my 6.2 Land Cruiser set up and wondering what size tire to go with to get my rpm in the best range. My first highway trip I got 20 mpg going 65 mph at probably around 2100 rpm (no tach installed yet) I may consider the electric fans if it makes that big of a difference. Right now I have a plastic flex fan that is supposed to be pretty low drag also but not as much as no fan at all I am sure.
Rusty

31 sounds pretty high...

I'm still getting 23-25 highway depending on the day with my 6.2. Lowest still sits at 20-21. Just straight city driving I get about 10 mpg.

On the highway I've noticed that I get the best mileage at about 60-65. If I go 55 I get worse mileage, if I go 65-70 I get worse mileage. About 63 seems to be the sweet spot.

A 6.2 in proper tune with overdrive should have no issues going 85+ (not that I'd recommend it, but I know they'll do it no problem)... Cruising at 70 should be no issue at all. Maybe not with 4.10s though.

So switching to electric fans would get you an improvement of 6mpg --- or 24%. That seems a bit much.

I got 20 mpg in my converted Land Cruiser and I was pretty happy with that but would really like to get closer to 25 if possible? Hitting the right rpm with tire size I am hoping will make a difference just wondering if electric fans will really make much difference, anyone else have any figures? I have a bit of time in modifying my shroud and other things associated with the flex fan to get rid of it, plus it is just one less thing to worry about. I think at highway speeds it flattens out quite a bit so can it be that much of a drag? How about the A/C, was it on? I have the old style Delco compressor that takes quite a bit of power to run but it is not really noticeable driving when it cycles on and off, just wonder what difference all of these factors really makes. I guess I will have to start experimenting but will probably have to wait 6 months before I can try without A/C.
Rusty

I didn't just switch to electric fans, I slowed down about 10mph over what I normaly do.
Past fuel milage was 26 or 27 at this speed. Every thing I read said it is normal to get 1 to 3 more MPG once you ditch your belt driven fan. I don't think a 21'' fan is normal to start with.
I have logged several hundred miles getting 29mpg drafting behind large delivery trucks (not tractor trailers) at about 60mph.
My A/C isn't working at the moment.
I wish I knew what RPM I was at, Any one got any Ideas for a tach that works???
My truck has G01 standard axel gears, I have been told those are 3.08's but don't know for sure and I have a G80 posi rear. I also have a 2wd truck with a weak and useless TH700R4 with lock up converter.
The tires I have I got form a friend that replaced them with yokohamas on his toyota truck, he says he has never gotten fuel milage like he had with the good years but says the yokohamas are better in every other way.
Also if you read about my tires on tirerack.com people say things like "they suck on every thing but dry pavement", "they last for ever" and a few people have commented about them getting good fuel milage.
You might not want to use electric fans if you do a lot of off roading, I hear they don't like mud/water going through them while they are on.

I've never used a map program for figuring out my mileage. Just the odometer and the number of gallons to figure the mpg. As far as electric fans for off-road, a manual switch can turn them off when in water or mud.

Smitty

My odometer is a little off.

I recently installed and calibrated an electronic speedometer/odometer in my truck. I calibrated it vs. my GPS navigation unit for accuracy, and checked it against highway mile markers. Seems to be pretty accurate.

That sounds cool. Got a name or link to some thing like it?

The speedometer in my '79 Camper Special is off by quite a bit. When I want to figure mileage, I use one of the built-in trip odometers on my GPS. It's very handy and dead-on accurate. If you already have a GPS or can borrow one for a few days, it's a low-buck way to get a very good mileage estimate regardless of the speedo calibration.

I will look at my speedo and see who made it, I don't remember. I did it because my trans was not compatible with a mechanical drive, but it is really neat because it gets programmed, you don't have to physically change anything based on tire sizes, axle ratios, etc... And there are no calculations involved. You wire it up to the sending unit, then put it in calibration mode and drive exactly 2 miles. It counts pulses from your sending unit over that distance and figures everything based on that.

Going on a little 50 mile round trip in the morning, I will fill and refill at the same station and on the same pump this time.
I will do odometer +3% and yahoo maps this time for milage.

I will look at my speedo and see who made it, I don't remember. I did it because my trans was not compatible with a mechanical drive, but it is really neat because it gets programmed, you don't have to physically change anything based on tire sizes, axle ratios, etc... And there are no calculations involved. You wire it up to the sending unit, then put it in calibration mode and drive exactly 2 miles. It counts pulses from your sending unit over that distance and figures everything based on that.

I have a Dakota Digital unit in my '56 that is calibrated like this. It has sure made it nice since I have switched gearing and tire sizes a couple times over the years.

Smitty

I went on my little trip to day.
Got 22mpg. But 40% of it was stop and go morning rush hour city traffic, plus my truck is being used as a storage shed for about 300 to 400 pounds of crap that belongs to my friend. It was raining a little or else I would have off loaded it.
Last trip was unloaded with very little city driving.
If I could have cut out the stop and go city driving I would have still gotten high 20's.
I also wanted to see how high I could get the EGT to go, so I left black smoke for about a mile. Yes bad for milage, but so hard to resist when you have a new EGT meter to abuse.
Yahoo maps and the corrected odometer were all most identical.
22mpg was close to what I would get driving pure interstate.
The EPA combind average rating which just happens to also use the 40/60 (city/highway) driving situation that I found my self in today is 18mpg. And 15/22 (city/highway) for a govt. rating. I all ways got about 17/24-25 (city/highway) after ram air and turning up the injector pump. That would make my previous combind 40/60 average 19.8mpg, now its 22mpg.
So this is good. Looks like my unloaded high way only milage will be in the real high 20's and not low 30's like the inital test, that is what I get for using a different fuel pump I guess.
Drafting will get over 30 no doubt.
A standard trans might get me over 30 with out cheating, but not any time this year.

So how much improvement on mpg do the electric fans actually make?

Try altering your aerodynamics and see what a difference that makes. DieselPower magazine took a roll of duct tape to a 1 ton extended cab Dodge dually and through careful driving habits pulled almost 31 mpg. I'm guessing you can do a lot better than 22 mpg if you try!

I don't think 50 miles is much of a test, there are alot of variables that could have taken place in that 50 miles that would be averaged out over 3-400 miles. I only check my mileage after nearly emptying the tank.
Rusty

Combind city and highway milage looks like it is +2mpg so far.
My guess is that straight high way will be a little more.
Wont be doing any high way trips untill July.
The fans stay off about 99% of the time just like I thought they would.

Good thread! Great info! I hope to do something with electric fans in the future to squeeze some more mpg.

So far, in my 93 below, I have gotten a best of 24.9 and 25.5 mpg - neither being all highway - but a good amount. But both have been with highway miles at ~ 70 mph which is ~ 2000 RPM. 2000 RPM is supposed to be the sweet spot for the 6.2. I will keep the auto in D, third, when in town at 35 to 45 mph to keep the RPMs closer to the sweet spot - 2000. The 24.9 was prior to the mods below. I have only had the truck a few months so it is too early for me to have a good test group and it will probably be months before I have some predominately highway miles to get a good read on highway mileage.

I have gotten a best of 19.9 to/from work but I expect to do much better than that since I have fixed the fuel leak and done the mods and I am doing less stop and go around town and more just to/from work.

Keep us posted, if I can pick up 2 mpg I will go electric. My only highway trip so far was right at 20 mpg but I am just starting to play with it, would love to hit the 25 mpg mark!
Rusty

I have an electric lawn mower, it draws enough wattage to make 1.3hp (its rated 1hp for some reason). It takes that to spin the 19'' grass cutting blade at 4200RPMs no load and its little thing.
I bet it takes several horse power to spin that 21'' 5 bladed thing 1500rpm (if the viscous clutch is 75% efficient when the engine is turning 2000rpm).
My camaro is next.
It gets 12/25 (city/highway). It has a straight belt driven 9 blade 19'' fan.

I have a flex fan (the plastic one) that is supposed to flatten out at speed accomplishing a similar effect, I am sure it is not as good as electric but it only cost about $20. I guess I could do a little research to see how much HP it requires to turn it at 2000 rpm. Keep us posted on your mpg figures over and extended time.
Rusty

The fan on the camaro is aluminum sheet metal bladed and should do that. But its not needed at high way speeds at all.
I have gone through many tanks of gas doing nothing but driving to work and home, when I only do that my car gets 12.5mpg.
My guess is driving like that, if I switch to electric I could pick up 1mpg. Because of faster warm ups (its only 2 miles to my work) and less drag on the engine.

Was your mechanical fan a clutch fan or a straight bolt-in one?

I have a spare electric fan I robbed from an 80's Citation for a spare for a Skylark which didn't need it - which itself is going to get junked soon - it wouldn't be a big deal to make some brackets to install one on a truck.

On my camaro its straight bolt on, the truck had a stock clutch fan.

Ok I bought a damned $20 'thermostat switch' form summitracing.com that turned out to be a gauge sender (it ohm checks at 350 give or take when its hot or cold).
But I went to auto zone and got a "radiator fan switch" for a 1992 5.7L z28 camaro. This one ohm checks OL, so its open till it get hot, I am fixing to put it in a pot of water on the stove to find out what temp it closes at. It may close above 212'F. If it comes on above the boiling point I will stick it on my truck and just drive around till it comes on.

I have a flex fan (the plastic one) that is supposed to flatten out at speed accomplishing a similar effect, I am sure it is not as good as electric but it only cost about $20. I guess I could do a little research to see how much HP it requires to turn it at 2000 rpm. Keep us posted on your mpg figures over and extended time.
Rusty

Those things are junk and sap a ton of power. A Hot Rod mag tested fans years ago on a dyno and the looser-the flex fan metal or plastic, winner was the clutch fan as when its not being used, IE proper engine temp, it saps no HP.

So make sure it freewheels at normal engine temp or its costing you money or switch to electric. I switched on my old Dodge B250 and it didn't net me squat for MPG, just a quieter engine.

My original intention was the original fan clutch but there is not room for it between my radiator and engine so I was stuck with the decision of flex fan or electric. I decided to try the flex fan because it was easy and cheap and no big lose if I decide to trash it. I am still considering an electric set-up, just waiting to see how the flex fan does now that it is getting hot. Do you think that a properly sized electric fan would cool better than the flex fan? I would love to increase the power as well but cooling is foremost.
Rusty

i liked the idea of a flex fan with an old chev gasser i had, until the blade flexed off and went threw the hood. it was a rough ride home with an unbalanced engine

Temperatures can rise quickly when you go up a steep incline in 3rd or 2nd gear in the heat. But I didn't notice the fan kicking in, so an electrical fan may suffice or even be advantageous in most circumstances --- until you really need the full airflow the clutch fan can provide. If you have A/C and make it so that the fan helps the condenser, like turning it on whenever the compressor clutch is locked, that may be a very nice setup ... at least until the electrical fan fails ...

I have 4 electric fans total. 3 will be automadic with manual back ups.
So there is no one point of failure, if the belt fan goes some how, you're screwed.
1 fan is the 16'' puller, turns on about 220'F also has a switch back up. Beside it there is another 12'' puller wired the same way but on a different circuit. The 3rd fan is a 12'' pusher on the A/C condencer, I will wire that to a relay powered off the A/C clutch power and have a manual back up. The 4th fan is the heater fan, its little but it pulls a good bit of heat off the engine.
Might need a bigger alt to run every thing.
If you can keep going faster then about 35mph you wont need fans at all thanks to the giant ass radiator they put in our trucks.

Sounds cool :) Any chance you can take some pictures? I'm still thinking about adding an electric fan between condenser and radiator the help the A/C and to be turned on manually when 4wheeling ... How do you install a fan there, did you make some kind of mounting bracket?

What's the heater fan?

Did you try going up a steep road in 3rd or 2nd gear for a few miles with ambient temps at about 100F and the truck loaded with a ton of camping gear?

My original intention was the original fan clutch but there is not room for it between my radiator and engine so I was stuck with the decision of flex fan or electric. I decided to try the flex fan because it was easy and cheap and no big lose if I decide to trash it. I am still considering an electric set-up, just waiting to see how the flex fan does now that it is getting hot. Do you think that a properly sized electric fan would cool better than the flex fan? I would love to increase the power as well but cooling is foremost.
Rusty

Flex fans cool ok, are you using it with a shroud?

A properly setup electric setup is more efficient, my heavy B250 van uses one and towing 6000 lbs, never overheats. I also have a good sized one on my stock rad Minivan and it runs cool in the city, :D

i liked the idea of a flex fan with an old chev gasser i had, until the blade flexed off and went threw the hood. it was a rough ride home with an unbalanced engine

Yep, there also deadly, many a mechanic has been injured and some killed due to them, :(

Temperatures can rise quickly when you go up a steep incline in 3rd or 2nd gear in the heat. But I didn't notice the fan kicking in, so an electrical fan may suffice or even be advantageous in most circumstances --- until you really need the full airflow the clutch fan can provide. If you have A/C and make it so that the fan helps the condenser, like turning it on whenever the compressor clutch is locked, that may be a very nice setup ... at least until the electrical fan fails ...

They can but a proper rad with the right size fan is fine, look at alot of OE's, most run electric now.

What type of electric fans is everyone using? I shopped for new fans and the AutoZone type generic fans were pretty cheap but if you went name brand you spend big bucks! Are they really any better? What type of thermostats are used?
As far as the flex fan breaking, I have a plastic model, not the aluminum. I bought it at a race shop and they said they are indestructable, they don't sell the aluminum ones anymore since they had too many come apart. Plus the plastic models are only about $15, couldn't pass that up and it is cheap enough I won't mind tossing it to the side when I get the electric fans.
Would love to see some pictures
Rusty

You can use radiator fan switchs form varrious other cars and trucks. Or get a fan switch kit from summit.

I got 18mpg with all most all city driving. That includes a "high way" trip that took over 2 hours to go 22 miles.
Out of the 27 gallons of fuel I burned 2 gallons were vegetable oil and 1 gallon of used hydraulic fluid.
The next tank will be made up of a lot more vegetable oil not that it is getting hotter out.

I have yet to put electrics on the diesel put i switched to electric on my nissan pickup and I gained almost 10 mpg. I was getting 14-15mpg now I am getting over 20. on the highway it has shot the mileage up too as the mech fan is still a load on the engine when not "engaged", with the electric one not kicking on at all. it hardley ever runs.

Ok, time to go electric. I was sitting in line at a drive through window to pick-up dinner tonight and it started getting hot. It did fine for about 10 minutes, stayed around 200º then it started inching up to about 220º. It didn't go any above that but I am afraid it would have. It was fairly cool and I didn't have the A/C running. I am thinking about 2 puller fans and 1 pusher fan wired with the A/C. What temperature should I get the two fans to switch on? The other strange thing, I am running a WVO blend and as the engine started getting hot it started surging. Not sure if that is related to the WVO but is there a reason why it would start to surge when hot? It cooled down quickly once I got moving again so I am pretty sure the radiator size is fine. I also noticed on the highway that when I turned off the A/C the engine temp would go down about 10º, the fan probably doesn't rob as much power but it would be nice to remove as much drain on the engine as possible.
Time to start shopping for fans!
Rusty

For got to add, My mother in law was "driving" the truck for a week also -:t . Her idea of driving left me with a flat tire and possible warped rotor.
I was stuck in stop and go trafic again on the interstate today, I left the fans off to see if my new real fan switch would kick it on. It never came on but stayed around 200'F in 80'F heat.

^^^

oil pan 4, great thread.

What brand of fan did you go with?

Junkyard, or new? If it is a junkyard peice, do you know what vehical you got it from? Shroud also?

With recient climbs in temps here. I've noticed my trucks temp rising from about 200 to about 215. It never really went that high before.


Thanks,

Doug

I got new fans off ebay. I bought a 3 pack of 12'' fans with seimens (or how every they are spelled) motors and I picked up a decent looking 16'' fan off a guy that sells a lot of car parts and had a 100% positive feed back.
I built the shrowds out of 26ga galvanized sheet metal, by hand basicly.
When its 80'F out I leave the fans off and it looks like my truck gets up to about 210'F in mild stop and go traffic.
As long as you can keep moving faster then about 30-35mph you won't need the fans.
The biggest hill around here is the draw bridge on I-264 in Portsmouth, I have been stuck in the tunnel before the bridge in stop and go traffic, with one fan wired up. About the time the truck got to 220'F (no fan) I started moving up hill (I may or may not have hit the fan, cant remember), buy the time I got to the top it was going back down to 200'F.

Thanks for taking the time to answer my questions.


Is there by chance you know the CFM ratings on those fans?


I don't believe my fan is doing a damn thing...but robbing power. It just seems like when the thermostat opens up, it goes back down to about 200*.

Thanks again,

Doug

You're in PA, of course the only thing its doing 99.8% of the time is robbing power.
I rarely need mine. You will never need them on the high way and wont need them as long as you can keep moving.
I believe this is just like my 16'' fan:

Staff edit: non-supporting vendor link removed

Here are one of my 12'' fans, I believe it is rated to move 1250cfm..

Staff edit: non-supporting vendor link removed

What temperature should I set the fans to switch on/off? I am not sure what temperature the engine likes to run at but on the highway mine seems to run around 180-200 with a 16" flex fan depending upon hills and A/C. It ran a bit hotter today during the day, probably around 200 the first 30 minutes of my trip but it was probably about 92º and I had the A/C on, as the weather cooled in the evening it dropped to about 180-190º. The temperature seems to drop about 10º with the A/C turned off. I am wondering if it might drop a bit more without the flex fan? I really don't think the flex fan does much at highway speed except rob a bit of power. It actually does fine in stop and go traffic but sitting at a stand still for about 10 minutes the temp starts rising and scares me a bit, I am still new with this engine and don't know what temperature is too hot. I am thinking about an adjustable thermostat, just need to know what temps to set it?
Rusty

I have a temp switch I pulled off an Izusu diesel. It was a stationary engine that drove a rotary air compressor and a hydraulic pump. The switches job was to shut the engine down if it reached 222'F.
My other switch is a radiator fan switch for a 1992 Z28 camaro, I don't know what temp it comes on at, I bet is close to 220'F. You can pick up one of these for $4 at auto zone.
You can pay $40 for a summit fan controler, it turns on 200'f and off at 180'f only problem is when it comes on it likely won't shut off untill you turn the truck off and let it cool.
I use a manual switch for the most part, the fan switches are for it I am not paying attention to the temp gauge and the engine temps sneek up on me.
The 6.2 regulates its temp very well with very little air flow.

What temperature should I set the fans to switch on/off?

Keep the coolant temp at 195--200F. The fan clutch seems to kick in when the coolant temperature is already at about 220F --- that's rather late.

If you are overheating at idle after 10 minutes, something is wrong. Diesels don't generate much heat at idle and cool down.

Coolant temperature can go up a bit after driving at highway speeds and then idling because there is hot coolant in the system that suddenly isn't cooled off so fast because there's not much airflow anymore. But the increase in temperature is minimal and you see it within maybe the first 5 minutes of idling.

Here are one of my 12'' fans, I believe it is rated to move 1250cfm..


The 12" would fit for the condenser? How do you install it? Did you make a mounting bracket or a shroud for the fan on the condenser?

I think the problem is that my radiator is a bit too small. I am using the toyota radiator, it is about 30"x17". I have heard from other people who have done this conversion that the stock toyota radiator works fine and it runs almost too cool on the highway so I am hoping it will be ok. It is a new radiator so I am sure it is good. I found out after installing it that it is only a 2 core radiator and the older ones were 3 core and cool a bit better so I might put a 3 core in it if the electric fans don't help. I just ordered some dual 13.5" flex-a-lite fans that put out 5600 cfm that I am hoping will fit. The dimensions given will fit but I have exactly 4" of clearance between the pump and the radiator and it says it is 4" thick, may have to do a little fabrication!
When the engine gets hot after sitting a few minutes it only takes about 30 seconds at 20-30 mph to get it back to around 180-190º again so my feeling is that if the fans can move close to the same amount of air as 20-30 mph it should stay nice and cool.
I hope to find out soon!
Rusty

One 12'' fan is just under the grill, for it I built some little brackets to hold the fan just above the condencer. So far it is the only pusher fan I have.
The 16'' and another 12'' have their own shrowds and are pullers.
When all 3 fans are going I can put my hand over the grill and feel the air being drawn in with battery power only. If I had the truck running and a few more volts in the system it would draw even more air.

Hmmmm ... If you use a fan as a puller, is a shroud a must or might it work without one (behind the condenser)? Even if I could make a shroud and put it behind the condenser, that would block the flow to the radiator. With the oil coolers in front of the condenser, I can't fit a pusher without making a new grille that would have more offset from the condenser. Hmmmm ...


BTW, do they make electric fan clutches (that replace the viscous clutches) that could be used?

http://www.********************.com/showthread.php?t=1635
That is a little on electric clutch fans.

If your going to use a 12'' fan as a puller on a huge radiator like whats in the 6.2 I think a fan shrowd would make it work its best.

******** means its the diesel towing resource

If your going to use a 12'' fan as a puller on a huge radiator like whats in the 6.2 I think a fan shrowd would make it work its best.

It would only be for the condenser --- I'm thinking of eventually picking up a fan from a junkyard and somehow put it behind the condenser to help the AC. I'd wire it with a switch to turn it off or on or have it come on automatically when the compressor clutch engages.

I've never looked at one of those fans closely so I don't have a good idea how to do it --- I'll probably just have to get one and then see what I can do with it.

Any idea which cars used 10" electrical fans?

Puller fans are all most all ways more efficient at moving air. The only pusher fan I use is on my trany cooler and it's 10' SPAL on a manual switch. One problem I have had running electric fans on stuff is much higher under hood temps cooking wiring. The further you go back in the engine compartment the less air there is cooling stuff. I've had very serious fire wall wiring damage and had to re route it away from the back of the engine for it to survive. Next has been poor AC performance at low speed , NA if ya don't have it. As for shrouds they do help pull air over a bigger area but have to have blow doors installed for higher speed other wise it's a big restriction. These blow off doors are just spring loaded flaps on the back side of the shroud that open up as air pressure builds up in the shroud. Are these fans running all the time or are you using a thermostat of some kind? And on a side note louvered hoods and fenders were used on rods not for looks but to get heat out of engine compartments.

My 6.2 with electric fans doesn't get nearly as hot under the hood as my Z28 with a straight belt driven 19'' fan.

Little compact SUV's some times have little fans (10 or 12 inch maybe) up front to push air on the A/C condencer or trans cooler.

I have been working on my dual 13.5" fans today, I knew they were going to be a tight fit but had no idea. I am having to make some mods to make them fit but it is finally in and hope to get it all buttoned up tomorrow and put some miles on it and see how they do. It is getting hot here now (mid 90's) so it will be a test. I think my flex fan probably wasn't cooling well because the shroud was such a poor fit. I also noticed the radiator I am using is only a 2 core, there is a 3 core available but the 2 core is thinner and it gives me a little more room to clear the water pump (every little bit helps!)
Hope to post some good news tomorrow.
Rusty

Got my fans finished up today. Took it around the block just to get it a bit warm. Right now they are set to come on at around 190º. They have a controller built into them so they come on at 60%, if the temperature goes up the fans speed up to 100% by the time it goes up another 10º. I parked in the driveway for about 10 minutes and let it idle the fans came on a couple times for about 20 seconds then shut off. Next I turned on the A/C, the fans are wired to come on with the A/C. After about a minute of running with the A/C on the engine temperature dropped to about 170, the outside temperature was probably mid 80's so not really hot but a pretty good test. I have since removed the wire so the fans no longer come on with the A/C, I will just let them cycle on with the engine temperature and see how that goes. It is just a simple matter of plugging the wire back in if it starts running hot with the A/C on but I would rather not have the fans running all the time with the A/C on, especially when on the highway they aren't needed. Overall my impressions of the Flex-a-lite are great. The kit was complete with everything needed, the instructions were really good and if it hadn't been for making mods to the front end and fan shroud to get them to fit it would have been a pretty simple job. They were expensive but $500 for peace of mind to me is a small price to pay.
Can't wait to get it on the highway and see if there is any difference, or the drive thru window at 100º for 10 minutes (both are coming soon).
Rusty

The drive throughs are so slow here I all ways shut my truck off.

They are slow here too, I picked up lunch at Chik-fil-a for my daughter today at noon so you can imagine what the line was like. I intentionally left it running just to see what the temp would do. I was in line 12 minutes and it never budged off of 190º, the outside temperature was probably about 90º, I love these fans! No more worrying about getting stuck in traffic and overheating.
Rusty

Drive throughs are funny, they can't exactly hear me and I can't hear them with the engine running.

Good to hear that your fans work, though :) How does the alternator hold up when you are crawling through the desert in 4low for 6 to 8 hours on an extremely bumpy road? And are all these fans ok for continuous duty?

Mine are continous duty.
I bought a 2wd truck for long distance road trips, the electric fan mod isn't for every one. My belt fan was just wasting fuel 99% of the time.

They recommend setting the fans up to be on when the A/C is switched on so I would think for alot of applications that would be continuous duty. The new models of these fans only run at 60% unless the engine continues heating up, I don't think my fans have probably ever gone to 100%. I had it wired at first to run continuously when the A/C was on but it actually got too cool that way so I removed the wire. Right now it just stays within about 5º of 190 all the time, still quite happy with them, no more worries! I would think they would do fine crawling for several hours through the desert, they appear to be sealed really well and well built, I am impressed with the quality of everything, again they were expensive but I really want a vehicle I don't have to worry about so spending a little more money doesn't bother me.
Rusty

That's good to know --- if I put one on the condenser, I don't have to worry how much it needs to run.

Rtarh20, the current the fans draw could be a problem. 30 amps maybe? With the engine just above idle, I don't know if a 75amp alternator would supply that. However, I've seen a CS130D alternator, rated for 100amps, putting out 50amps at idle and 105 at about 1800 or 1900 RPM (while installed on the engine).

If the alternators are all pretty much the same, a 75amp one may produce 30 to 40 amps under those conditions. That would be tight but might still work if you try to save power: No lights, no radio, no A/C ...

how many hours you plan to idle? its not really too much of an issue, got two batteries for back up till you start moving and they charge

how many hours you plan to idle? its not really too much of an issue, got two batteries for back up till you start moving and they charge

What I have in mind is 6 to 8 hours driving just off idle in 4low. If you do some math:

30 amps for fans, 3 amps fuel shutoff solenoid, 15 amps for blower motor, 10 amps for A/C compressor clutch: about 58amps continuous draw. The alternator may produce about 35 amps. The batteries would have to supply 23 amps for 7 hours.

Batteries are 2x110ah (in my case), so you got 220ah. 23 amps for 7 hours means drawing 161ah from the batteries. Since they are starter batteries, you are not supposed to discharge more than 1/2 their capacity, and there seems to be some agreement that they are usually only about 80% charged to begin with. Consider the heat under the hood, it lowers the alternator output, and I'm not sure about its effect on the batteries.

It means you can probably do it with the A/C and the blower motor turned off. It also means that you will eventually be unable to restart the engine after stopping in the middle of the desert to take some pictures or the next morning after camping over night. If you are stuck, it can take a few days before someone comes along, and your cell phone doesn't work because you are too far away from everything. If you don't have jumper cables, you are somewhat screwed even if someone comes along ...That's why they tell you to bring lots of water when going into a desert ;)

Like Oil pan 4 says, electric fans are not for everyone.

doesn't matter how much rock crawling you do, you'll be going over idle enough of the time to get some charge in there. the AC pusher fan should be wired with a relay to the clutch fan so it only comes on when needed. when i'm parked with lots of spot lights on and or using the winch, i turn on the manual fast idle, especially before shutting it off to make sure its charged up.

Yeah, I wouldn't worry about a fan on the condenser, only if it was electric fans only. If I'm going to install that fan, I'll make it so that it has three settings: off, on/off with clutch, on.

Me, I'm lazy... I'd wire mine into a temp sensor. If I were going to install electric fans anyway.

I just about found the limit of my 1 fan. Friday I was in stop and go traffic, about 95'F with a slight tail wind. The truck hovered at about 210'F most of that time.
As I moved and had the wind coming form the front or side, the temp was normal.
Any thing over 25-30mph was enough to cool it with out fans.
I think I will wire the A/C condencer pusher so it can run with the truck "off" if I want it to, that way I can cool the coolant in the radiator when stopped.
I may go to Texas this July, but no where near Austin.

I may go to Texas this July, but no where near Austin.

Cool --- we have a lot of wind and heat here to test your fan. Be sure to bring your clutch fan as a backup ... ;)

More seriously, 210 is a bit hot. Doesn't the fan bring it down to 200, or isn't it setup to do that? Going up an incline can suddenly give you another 15--20 degrees, so starting out at 210 would eventually bring you (close) to 230.

That was the only time it got up to 210'F other then when when I forgot to turn the fan on. Most of the time wind form any direction is good. Only time it hurts is when it is blowing form behind.
Diesels can take the heat better than a gasser, we don't have to be conserned with pre-ignition like they do. You know how they are all ways useing 160'F and 180'F thermostats.
My truck use to get up to 230-240'F when it had a junky $1.99 elcheapo thermo stat on it (and that was back when I had the belt driven fan). So far it hasn't gotten over 220'F even with the fans off. The fan switches I have should kick on about 220'F but I have not herd them come on yet.
Also my cooling system is in great shape, I have that high flow therm that is only a year old and a new radiator that is about 1-2 month old. The cooling system is now filled with Low tox to the tune of about 2/3's coolant to 1/3 water. My flushing operation lasted about a week because I didn't get to finish it in one weekend because of rain.

I think I have an el cheapo thermostat, could be causing some of my problems. What type thermostat should I get?
Rusty

Go to advanced auto and ask for a high flow thermo for an 1984 6.2 suburban.
Get the most expensive one, they will likely have to order it. It should be less than $10.
Go on summitracing.com and look up high flow thermostats, that way you will know what it looks like and don't get ripped off.

I've used the cheap thermostats for years and never had a problem. They don't last very long, but functionally they seem fine...

I never had a problem with my cheap thermo untill I went to maine for a few weeks and encountered moutains.

I will try to find one, I guess the problems would be the fact that it stops opening so I would know it isn't working by the fact the engine overheats?
Rusty

The problem that I was having with elcheapo is that I don't think it reacted fast enought to temp increases and then didn't allow enough coolant to flow when it was to hot.
It was about 95'F to day I drove the truck home hot, and put it in the drive way with the one fan going then I poped the hood and connected the other 2 fans to the battery, shut the hood and let it idle for 20min. The temp went down to about 190'F and stayed there. I could put my hand over the grill and feel the air being drawn in.

That was the only time it got up to 210'F other then when when I forgot to turn the fan on.


Uh, now that you mention it, it doesn't seem adviseable to make it so that you can turn the fan off ...


Most of the time wind form any direction is good. Only time it hurts is when it is blowing form behind.


Once I drove about 10 miles to the parts store with the fan taken off to get a new fan clutch. On the way back, I was sitting in traffic for a few minutes, and it started to overheat so that I had to stop and put the new clutch on. So driving without a fan can make it overheat quickly.


Diesels can take the heat better than a gasser, we don't have to be conserned with pre-ignition like they do. You know how they are all ways useing 160'F and 180'F thermostats.


Well, I don't know gassers. I've had a few but never worked on one except for changing spark plugs on one. Diesel is cheaper than gas throughout Europe, and you get better mileage with Diesel. Diesels are for driving ... Sure you can drive a gasser, but it's somehow not the same.


My truck use to get up to 230-240'F when it had a junky $1.99 elcheapo thermo stat on it

That's too hot ...

I think I have an el cheapo thermostat, could be causing some of my problems. What type thermostat should I get?
Rusty

The ones I got were from autozone, and they work fine so far. High flow might be better, though.

The high flow thermostats do have a different design, and will flow more when open, no doubt about it. However, even towing in the middle of the summer I've never had overheating problems with the cheap thermostats. Like I said, though, they don't last very long either. When they fail (which is frequently) they break and "open" so the truck just never warms up.

That is good that the thermostat stays open when it fails.
Now back to the original post about electric fans and mpg. I made my first trip with the electric fans and there was no difference in mpg compared to the same trip several weeks ago with the flex fan, but several weeks ago I did not use the A/C and this trip I did so........how much does your mpg drop with your A/C on? That may be the savings with the electric fans in my case. I really can't tell a bit of difference as far as power is concerned but I do like the electric fans in the fact that they are only on when needed, I think they might help it warm-up a bit faster in the winter.
Rusty

I have been told that A/C can cost any where form 1mpg to 10% of fuel economy. I think most of us have the giant A/C compressor so it would be up there compared to little A/C's found in cars.
Diesel power mag published an article on converting to electric fans, they gained form 1 to 3 mpg in the tests.