Can the air controller be fixed? My air conditioning has never really worked right. Blows cold but doesn't blow hard all the time...it will get loud and then less air comes out.

Does this sound like the controller?

Can it be fixed?

I believe the air control is run by vacuum servos, you probably have a vacuum line leaking under the dash. Anybody else have more detail?

The controllers are subject to failure. They are electronic, not vacuum iirc. Start with a new controller and see if that fixes it.

Can the air controller be fixed? My air conditioning has never really worked right. Blows cold but doesn't blow hard all the time...it will get loud and then less air comes out.

Does this sound like the controller?

Can it be fixed?
__________________________________________________ _________

The controller can be fixed if your an electronic guru with the proper diagnostic tools. the controler has a couple of chips and a bunch of resistors and such, so which part failed is the mystery.

Now when you say blows hard do you mean on max air or on regular A/C? Is it cycling between max air and regular A/c settings? The loud air noise, is it coming from the passenger footwell?
It could be as simple as a blower motor resistor or the blower motor going out.
Here are some photos out of a '96 GM book, feel free to use them or have posted in the "how to diagnostic" section.

__________________________________________________ _________

The controller can be fixed if your an electronic guru with the proper diagnostic tools. the controler has a couple of chips and a bunch of resistors and such, so which part failed is the mystery.

Now when you say blows hard do you mean on max air or on regular A/C? Is it cycling between max air and regular A/c settings? The loud air noise, is it coming from the passenger footwell?
It could be as simple as a blower motor resistor or the blower motor going out.
Here are some photos out of a '96 GM book, feel free to use them or have posted in the "how to diagnostic" section.

When set on max air it will blow hard for awhile and then get loud over in the passenger side footwell blower area and then the air coming out of the vents slows to a trickle...it is still cold though. Really aggravating! Seems to act up in spurts.

Thanks for the photos!

More than likely your freezing off over time, as a test switch off the air for a couple of minutes but leave the blower going on high to the vents, this will melt the ice build-up. Then switch the air back on to see if its back to normal.

I'm not sure if its an overcharge or undercharge that caused this to happen but my 00 does exactly that too.

CR is right about freeze over. That is usually a stuck pressure switch. Once the refrigerant pressure drops to a certain point, the low pressure switch turns off the compressor breifly until the evaporator pressure rises again. This is to prevent freezing up of the evaporator.

These compressors (when working properly) have tremendous capacity. They are designed for high heat load conditions. When you are running under a partial load condition (cool day, lower humidity) it has the capacity to freeze up the coil really well.

Amount of refrigerant charge in the system should not cause a freeze up situation with a pressure switch control on the system.

Check to see if the clutch on the compressor ever disengages when sitting at idle with the fan on low when it's cool outside. Notice if there is a frost build up on the lines coming from the evaporator or on the accumulator. These are indicators that the low pressure switch may be your problem. Best way to tell is with a pressure gauge. (Now don't ask me for the on/off pressure, 'cause I don't know) Someone with a manual may be able to clue you in on that.

It acts this way within a minute or two of turning the air on sometimes. Recently, more so! Just a month ago or two ago...when the weather was cooler, the air conditioner ran great. I thought it fixed its self. Of course when it would really be nice to have it (90's) it goes on the fritz.

My 95 suburban is doing the same thing. I replaced the controller with no change to the air flow. My air is cold as well but just don't get the air flow out of the vents. What initially made me change out the controller was that my max AC recircluation damper (the one in the passenger floorboard on the fan housing) would open and close itself on its own. I changed the controller thinking that it was acting up but it does the same thing with the new controller.
Just to give everyone an idea of the amount of air flow you get out of the front vents. I compared it to my kia minivan and I get more air out of the vents of the van with the setting on low than I do out of the suburban with the fan on high max A/C. The fan is spinning fine and is not slipping on the shaft. I was able to stick my hand in the recirculation damper and feel the fan wheel spinning. It almost seems like the evaporator is completely clogged up and is not allowing the air to pass through. The air flow is the same no matter if you just crank up or have been runnng for an hour. So I don't think it is a freeze up issue. Any ideas out there. Is there anyone that has an A/C that will blow your hair with the fan on high or are these systems on the weak side. A side note the rear air works fine.

My rear AC works fine as well.

I remember way back when...I took the vehicle in while it was still under the warrenty. The service tech asked if I had a kitty, because the filter had kitty hair in it. Never had a critter in the vehicle. He said he cleaned it out and everything should be fine now and sent me on my way. I had it back a couple of more times and finally gave up on it. The compressor went out a couple of times...they did replace those. I recently did a vin search on my vehicle and nothing shows up. This particular dealer didn't even register my vehicle.
:rant:

Can the air controller be fixed? My air conditioning has never really worked right. Blows cold but doesn't blow hard all the time...it will get loud and then less air comes out.

Does this sound like the controller?

Can it be fixed?

Mine has always done, basically, the same thing, but only when the recirculating air button (or knob in MAX position) is pushed. If I keep it off of the MAX position, it doesn't do this. If I remember right, when I have it in the MAX position AND push the recirc. button, it doesn't do it quite as often.

I'm guessing mine is electrical because of this. Does yours do it in both of these positions?

SnowDrift

Mine has always done, basically, the same thing, but only when the recirculating air button (or knob in MAX position) is pushed. If I keep it off of the MAX position, it doesn't do this. If I remember right, when I have it in the MAX position AND push the recirc. button, it doesn't do it quite as often.

I'm guessing mine is electrical because of this. Does yours do it in both of these positions?

SnowDrift Yes, there is something funky going on with the recirculation button. Right now whether it is pushed in or is in the out position the light is on. I can't seem to get it to cut off, except when I reduce the fan from MAX...then the recirculation button light will go out.

Mine is the same way, recirc light is always on. I am about to the point I am going to take it to the stealership and tell them to just fix it. If I get anywhere with it I will keep you informed. Sure wish someone has solved this issue in the past and could give us some direction.

Yes, there is something funky going on with the recirculation button. Right now whether it is pushed in or is in the out position the light is on. I can't seem to get it to cut off, except when I reduce the fan from MAX...then the recirculation button light will go out.

Max automatically defaults to recirculate.

Max automatically defaults to recirculate.

Even when the button is not depressed:confused:

Even when the button is not depressed:confused:

Yes

I thought that maybe the recirulation button may be messed up...but if that is the way it is supposed to funtion then something else is goofed up.

So it still blows cold, but no air ( very little) out the vents. I really hate this type of diagnosing over the internet. couple of questions, Do you drive through a lot of dusty areas where the vents will blow out a plume of dust when you first fire up the blower? do you drive with animals inside you vehicle? do you get a really bad musty/mildew smell out of the A/C?
It may be that the evaporator inside the truck has one side caked with crud, retaining the moisture from the refrigeration process and then freezing up and not letting sufficient air flow over the evaporator coils.

So it still blows cold, but no air ( very little) out the vents. I really hate this type of diagnosing over the internet. couple of questions, Do you drive through a lot of dusty areas where the vents will blow out a plume of dust when you first fire up the blower? do you drive with animals inside you vehicle? do you get a really bad musty/mildew smell out of the A/C?
It may be that the evaporator inside the truck has one side caked with crud, retaining the moisture from the refrigeration process and then freezing up and not letting sufficient air flow over the evaporator coils.

No to all of the above.

When it gets noisy over on the passenger side footwell the air slows to a trickle out of the vents...it is still cold though, just barely blowing.

Where is the evaporator located. I could check to see if it has any crud on it.

When it gets noisy over on the passenger side footwell the air slows to a trickle out of the vents...it is still cold though, just barely blowing
Thats what happens when it freezes over, won't allow much air flow through it.

the evaporator is buried inside all of that interior plastic (read PIA to get to). one thing that leads to freeze over is either too much crud on the evoprator [B]OR[B] too much freon in the system bypassing the CCOT A/C system.

Thats what happens when it freezes over, won't allow much air flow through it.

I does it from start up(lately)...as soon as the vehicle is cranked up. Although it has acted as you suggest...run good for awhile (1/2 hr or so) and then the air doesn't blow as hard. But it has been ahwile since it acted like that. I can hear when it is getting ready to blow slower. It gets louder in the footwell and it sounds like the air can't make up it's mind which way it wants to go and then something happens and it sounds like the air gets redirected somewhere else...just not out the vents.

Well if it does it from startup and hasn't been run for a few minutes that might not be your problem then, especially if it runs like crap at startup and then gets better and then back to worse.

I had a redirection vent/flapper fall out on the floor of my Blazer, everything seems to work ok still though.... lol

I think me and mp4037 have the exact same issue. My question to the rest of you is how hard does your air blow when your A/C is on the highest fan speed. I barely get any air out of the vest next to the driver door and very little out of the passenger door. The other vents get a little more but still it is not near enough. My guess is the my evaporator is clogged up with dirt/dust collecting on the inlet side. I have had the suburban for a year now and it had always been this way. I do know that it had a rough life before I purchased it so it could have been in a lot of dusty conditions.

Anyone have instructions/experience getting to the evaporator. Taking all of the plastic off the dash is beyond my ability without having some guidance. Thanks.

My air blows hard to begin with but freezes over after a few minutes of operation depending on weather conditions. Turning the air off for a few minutes to thaw it out always works for me. I'm sure its half plugged with debris of some sort but i'm in no hurry to pull apart all that duct work.

I think me and mp4037 have the exact same issue. My question to the rest of you is how hard does your air blow when your A/C is on the highest fan speed. I barely get any air out of the vest next to the driver door and very little out of the passenger door. The other vents get a little more but still it is not near enough. My guess is the my evaporator is clogged up with dirt/dust collecting on the inlet side. I have had the suburban for a year now and it had always been this way. I do know that it had a rough life before I purchased it so it could have been in a lot of dusty conditions.

Anyone have instructions/experience getting to the evaporator. Taking all of the plastic off the dash is beyond my ability without having some guidance. Thanks.

I'd like some guidance, too. Plastic dash parts don't agree with me. Bolts and steel are fine.:(

From what I have read todate I would test the blower motor first. Hard wire the motor and run it for a while . Reduced air flow and noise sounds like a bad bearing in the motor.
Connect 12 volts to the purple wire feeding the blower motor. That will run the motor a full speed. Run the motor, while the truck is sitting, for several min. and see if the noise happens. If it does your problem is in the motor.
If there is no problem after a normal reaction time go for a drive with the AC on.
Freeze over generaly takes quite a bit of time, hour or more depending on humidity and temperature. Freeze over is a result of a low charge and can be checked by watching the compressor clutch while the AC is on, doors are open and the engine is turning at 1500 or above. If the clutch cycles on and off you are low on charge and this could cause a freeze over.

From what I have read todate I would test the blower motor first. Hard wire the motor and run it for a while . Reduced air flow and noise sounds like a bad bearing in the motor.
Connect 12 volts to the purple wire feeding the blower motor. That will run the motor a full speed. Run the motor, while the truck is sitting, for several min. and see if the noise happens. If it does your problem is in the motor.
If there is no problem after a normal reaction time go for a drive with the AC on.
Freeze over generaly takes quite a bit of time, hour or more depending on humidity and temperature. Freeze over is a result of a low charge and can be checked by watching the compressor clutch while the AC is on, doors are open and the engine is turning at 1500 or above. If the clutch cycles on and off you are low on charge and this could cause a freeze over.

Howie Wrote: Reduced air flow and noise sounds like a bad bearing in the motor.

It's not that kind of noise. It sounds more like a hurricaine...lots of wind. Just not coming out the vents.

SideNote: The recirculation button light would not come on today. Even when the button was depressed or not. Even when the air was on MAX.

MP4037,
Have you removed your controller for inspection? This is very easy to do.
1) remove the guage cluster bezel (the plastic piece around the guages/radio/ A/C). tilt the steering wheel all the way down and with your fingers start pulling the bezel towards you, it is held in with spring clips. disconnect the headlight plug. take your time pulling it off.
2) The A/C controller is held is held in by molded in clips (the slots on each side) Use a small screw driver and pry the clip to release from the dash assembly.
3) once controller is removed, check to see if the circuit board has any burn marks from a blown resistor or other component, also check to see if the circuit board has any visible broken paths.

If anything looks fishy on the controller, hit up a local wrecking yard for one, GM ran this style of controller for a few years on any full size pick up, tahoe, suburban and I believe astro van (not 100% sure on the astro van).

Feel free to call me 5:30-8:30pm pacific time if you have any questions, it'll probably be easier to hash out over the phone than typing. BTW I PM'd you with my home phone #

Ok MP4037 here is your answer,
Like I stated earlier in this post, my is doing the same thing yours is and I have already replaced the controller with no change is the operation of the A/C. I just got through cleaning my evaporator and it was filthy. The previous owner definately had a dog. There was hair, pinestraw, small pieces of leaves and everything coated with a thick coat of dirt. The fins were totally stopped up and upon cleaning I now get 4 times the air flow. Heres how I fixed it.

1st remove the glove box. Open the glove box, disconnet the catch wire which is on the drivers side of the glove box. It disconnects by sliding the connection tab forward in the slot. (It will be obvious how to remove it) then press the two stops at the top edges of the glove box which will allow to the rotate out of the dash. Finally pull up on the bottom hinges as you rotate the glove box out of the dash. Once you get the box rotated out to a certain point the bottom hinges will slide up and release.

2nd remove the blower cover. Easiest way (which is what I did and others as well) is first look on the bottom of the cover and slide the cover off of the plastic tab. Next remove the two motor wiring connection toward the top of the motor. (should easily slide off with your fingers or need nose pliers) Take a razor blade, exacto knife, etc. and cut the cover from the penetrations where the computer mounts to the very top of the cover. This will allow you to remove the cover without having to mess with your computer. (I recommend doing this as it will not hender reinstallation of the cover at all, It should have been designed this way to begin with IMOP). Now slowly work the cover off the motor.

3rd remove the blower motor. Motor easily removes with 5 screws. Once screws are removed pull motor out and rotate 1/4 turn to clear the dash.

4th clean the evaporator. The evaporator will be on the discharge side of the blower (going into the black plastic box toward the driver side of the vehicle) It will be a tight squeeze for someone with bigger hands. First I took my small 5 gallon shop vac hose and removed all of the loose dirt, leaves, and pinestraw. Next I took a old tooth brush and cut the handle in half. Taped the brissles and half of a handle to my middle finger allowing me to reach in the cramped area and gently brush the fins with my middle finger. I took the shop vac and sucked off all of the loose hair and dirt. Take is slow and easy as you don't want to bend the fins on the evaporator. After 45 minutes of brush cleaning I then took a garden hose with spray nozzle and flushed as well as I could. Be sure to make short blasts of water to allow time for the evaporator box to drain out the condensation drain. Also place a towel in the passenger floor board in case the evaporator box gets too full of water and seeps out the sides. Once the flushing is complete wipe the water out of the fan housing and reinstall ran. It is best to install fan temporary with a couple of screws and connect the wires and conduct a test run. It should blow much harder now. If not, reflush and try again.

4th reinstall all components in reverse order.


Hope this helps

Thanks for a taking the time to help. I'll will clean it out this weekend and see how it goes.

By the way no more funny damper opening and closing. My thoughts were as the evaporator begins to freeze due to lack of air flow since the fins are so filthy you begin to get such a positive pressure in the "air box" that it begins to force the "fresh" air damper open and thus forces the recirc damper closed and visa versa. Good luck this weekend. You will be happy with the result. I actually had to turn the temperature UP this morning with the fan on LOW. That has never happened before.

Well...your instructions are right on. One definitly needs to be a hobbit to work in this manner. I now see why the fellow who worked on this years ago just said screw it and stuffed everything back in...without some of the screws. Probably the toggle switch guy.
I have the blower out and can see the evaporator...and it definitly needs a good cleanin. Pine straw, black stuff, string, even a feminin pad...:damnit1: But no kitty hair!! It looks like the inside of a vacuum cleaner bag.

I'll attempt to clean this mess tomorrow when there is a bit more light. Brilliant idea taping a brush to your finger. I'm thinking of taping a hammer to mine at the moment and knocking some of that plastic out of my way.

Will that other piece of plastic that is in the way, will it come off ? It sure would make cleaning this thing a little easier.

I'm following this thread as well since I have the same problem... no air flow... of course mine is complicated by the A/C not working blah, blah, blah, but THAT is a seperate problem. Once I get air flow I'll work on the A/C.

I can attest for you MP4037 that getting the plastic out of the way is a lot easier than you think. I have the little plastic shards and pieces to prove it. Now if I can get it back together is a whole seperate issue. I thought I could just unscrew everything and get to it... No way. Screws are too far hidden. So I'll end up duct taping / gluing the pieces that came off back together and going the route prescribed...

Toothbrush... vacuum... hose... maybe a little compressed air....

Bill

Can you tape the toothbrush to the vac? Or somehow stuff the vac in there while brushing. It'll do a better & faster job if you can get both going at once:cool:

Where does all that stuff come from...I'm guessing from outside. It doesn't come from the passenger side floor does it? Seems as though there should be some kind of filter that could be changed to prevent this build up in the evaporator. ):h

I would like to blast some water from a hose through the evaporator like johnsonjwj did. I'm concerned that I may blow stuff through and this may clog the drain. Is this possible? At the same time i'm wondering if I could spray a little tile-x or something up in there(it looks moldy and caked on) without harming anything other than my lungs. I have zero knowledge about this setup other than what i'm discovering right now.

As for were this stuff comes from. If you remove the cowling in front of the windshield and look in with a light from the drivers side you will see the fresh air intake, with a 1 in high parapit, under a metal deck on the passengers side. It is common to see leaves built up against the edge of the parapit. Smaller leaves, pine needles, and just dirt will be pulled in and land against the evaporator coil.

Another common problem is for enough stuff to build up against the parapit as to allow water to overflow and flood the AC houseing during heavy rains.

If the dirt is dry while you have the cowling off a vacuum with a plastic pipe attached will reach in there. Once vacuumed if you flood the area with water the remaining smaller dirt will flow out between the body and the fender

Great stuff johnsonjwj and dhjunkie. This appears to have solved the problem. I just did a few flushes with water threw the blower on real quick and gave it a try.... and whooosh. lots of air. After a few flushes i was able to reach up in there and gently pull of lots of, what appears to be kitty hair. I have no explanation other than some cat must have been standing too close to the truck and got all its hair sucked off ):h Lots of hair. Really, if I had to guess some criter was probably laying on the truck at night throwing its hair down the cowling or where ever the fresh air comes from. After going through this and seeing how dirty it is I would really like to get the evaporator out and give it a super cleaning. Next Time.

Glad I could help. Now go drive around and not have sweat pouring off of your forehead. My air smelled a little like wet dog once I got through cleaning the evaporator so I sprayed some Febreeze in the evaporator (or I guess you could spray it in the fresh air damper with the A/C on) and the smell was resolved. I will probably die of cancer in 50 years but the wife likes the fresh/clean smell.

Can the air controller be fixed? My air conditioning has never really worked right. Blows cold but doesn't blow hard all the time...it will get loud and then less air comes out.

Does this sound like the controller?

Can it be fixed?

Sometimes plastic can get sucked into the blower and plug it. I've also seen leaves do it from the outer vent.

I've cleaned some with household hvac cleaner and it worked rather well it's some kind of acid. you spray it on and a few seconds later the whole core will be a ball of foam. after you rinse it off the core will look like new again. there are no name brands,but you should just be able to walk into a hvac parts store and ask for evap core cleaner. My gallon cost 6.00

I considered that too... It's simply called coil cleaner at an HVAC supply shop... It's really phosphoric acid... But I'd hate to think what that might do if it gets on the carpeting...

Bill

Make sure you get coil cleaner made for EVAPORATOR cleaning only. If you use condenser coil cleaner, you will smell it for months and regret it, although condenser coil cleaner will work wonders on the actual condenser and radiator.

Make sure you get coil cleaner made for EVAPORATOR cleaning only. If you use condenser coil cleaner, you will smell it for months and regret it, although condenser coil cleaner will work wonders on the actual condenser and radiator.

Will

Make sure you get coil cleaner made for EVAPORATOR cleaning only. If you use condenser coil cleaner, you will smell it for months and regret it, although condenser coil cleaner will work wonders on the actual condenser and radiator.

Will the Evaporator cleaner harm the plastic and rubber? Just curious.

Evaporator cleaner is a milder acid, and should not harm any of the plastic parts. Some of the stronger condenser cleaners if not diluted could easily melt or break down plastic parts. The unfortunate part about evap cleaner is it doesn't work as well, but is safer. Also, I am not sure about vehicle evaporators, but home A/C indoor coils have a coating on them that aids in draining condensation away, and strong acids will break down the coating. I have seen many indoors coils cleaned with too strong of an acid, and have chronic condensate leaks afterwords.

I had the same air flow quantity on my 99 suburban. If I am understanding your sequence of events correctly I would guess you have a leak in your HVAC blower system. The system needs to be sealed in order for you to get air pressure/ volume. You say it blows ok then when you here the noise by the passenger foot well it gets noisy but then air flow diminishes. I'm guessing it blows ok at first because your recirculating damper has not yet switched over. If this is true your recirculation air damper (located next to the fan motor by the passengers feet) used to switch from outside air (Low through High Fan) to inside air (Max[95 or newer] or Recirculation [pre 95]) is sticky.
After 6 hours and $13 I was able to fix my problem. It know blows great volume through all the vents. Here's what happened. The foam piece on the firewall that allows the A/C lines, Heater hoses, A/C water drain and one bolt to help hold the air box to the firewall was partially melted (Like 30% was gone). This melted foam piece is right where the down pipe for the turbo goes. In doing so this caused an air leak in the ducting. You actually have separate ducting for A/C and Heat.
My thought is you have a sticky recirculation baffle and an air box leak. I remembered this as a friend also had this happen on his 94 dually.

MP,

Sounds like problem is very similar to mine. It goes the same for the heat in the winter too. You could turn the fan all the way and not much more would happen than being on low. What I found was that the floor damper had shifted over and could not turn freely. This caused the spring loaded piece od $#@^ linkage to break. Try looking under the driver's side of the dash, towards the firewall for the servo motor and linkage that controls you vernts. It is easier to find if turn your vent select nob while looking. Good luck, hope this helps.

Sean

I had the same air flow quantity on my 99 suburban. If I am understanding your sequence of events correctly I would guess you have a leak in your HVAC blower system. The system needs to be sealed in order for you to get air pressure/ volume. You say it blows ok then when you here the noise by the passenger foot well it gets noisy but then air flow diminishes. I'm guessing it blows ok at first because your recirculating damper has not yet switched over. If this is true your recirculation air damper (located next to the fan motor by the passengers feet) used to switch from outside air (Low through High Fan) to inside air (Max[95 or newer] or Recirculation [pre 95]) is sticky.
After 6 hours and $13 I was able to fix my problem. It know blows great volume through all the vents. Here's what happened. The foam piece on the firewall that allows the A/C lines, Heater hoses, A/C water drain and one bolt to help hold the air box to the firewall was partially melted (Like 30% was gone). This melted foam piece is right where the down pipe for the turbo goes. In doing so this caused an air leak in the ducting. You actually have separate ducting for A/C and Heat.
My thought is you have a sticky recirculation baffle and an air box leak. I remembered this as a friend also had this happen on his 94 dually.

Thanks for the input. Cleaning the evaporator definitly fixed my problem. It has been a few days and no problems whatsoever with the AC. Blowing harder and cooler than I ever remember. 10 times more air.

Now the truck itself is broke...go figure:mad: