hey guys, i had the ac worked on a few years ago by the dealer. they changed a solonoid on the canister and recharged the system.

it worked but not really like it should. it would get cool but not super cold like some guys on here are talking about. if i put it on auto and set the temp at 60 it would blow on max for a while then bump down the fan speed for a few mins (probably half speed) then back up to max again.

anyways today it was 105 out and it was blowing out some not so cold air.

i turned it on again on the way home while it was 96 out and the air was cool but not cold.

any ideas on what it could be? should i buy one of those recharge kits ans see what pressure it is at? maybe add a little?

thanks

Here this will help it blow colder. http://www.dieselplace.com/forum/showthread.php?t=159270&highlight=colder&page=2 But you can see what kinda of pressure the system has. Also you might need to change the orphas. I think thats hows it spelled.

i did remember reading that thread a few months ago. how cold is the ac suppose to be at idle and then at 60mph?

also i might buy one of those recharge kits tomorrow and see what my pressure is.
any idea what psi it should read?

also what is the orphas? never heard of that

I found the correct spelling "Orifice". Its like a inline filter and something eles Im not forsure. Its at a connection going to the compressor. So to change it you have to release all the pressure in the system.

hey guys, i had the ac worked on a few years ago by the dealer. they changed a solonoid on the canister and recharged the system.

it worked but not really like it should. it would get cool but not super cold like some guys on here are talking about. if i put it on auto and set the temp at 60 it would blow on max for a while then bump down the fan speed for a few mins (probably half speed) then back up to max again.

anyways today it was 105 out and it was blowing out some not so cold air.

i turned it on again on the way home while it was 96 out and the air was cool but not cold.

any ideas on what it could be? should i buy one of those recharge kits ans see what pressure it is at? maybe add a little?

thanks
Maybe it's the brakes? J/K
Seriously, I think there's enough info here to answer your questions http://www.dieselplace.com/forum/showthread.php?t=256363

when in proper working order it should freeze you out. The GMT-800's have awesome AC IMO.

ben

at 90 degrees outside, mine is putting out around 45-50 degree air...i have a thermometer in the a/c vent.

I had my ac fixed under GM warranty a few years ago...definitely made it run a lot colder.

im going to get a thermometer and one of those ac psi gauges. that way i can get you some real numbers.

well i ran a quick trip around town and my thermometer read anywhere from 44-50 at max output. outside temps are in the low 70's.

i was going to try and get one of those psi gauge sets but the parts store that was open wanted a good bit of money for them

when it warms up this afternoon ill drive around again

also, i might give that bypass a try. only problem i see with that is some mornings its cold here in MT and hot in the afternoon. i would have to get out and open it then shut it later on..

well i ran a quick trip around town and my thermometer read anywhere from 44-50 at max output. outside temps are in the low 70's.

i was going to try and get one of those psi gauge sets but the parts store that was open wanted a good bit of money for them

when it warms up this afternoon ill drive around again

The Napa near one of my jobsites had a full gauge set, including the little can tap for $65. I woulda bought it instead of the ones i have.

well i drove around a lot today. temps were in the high 80's and low 90's.
i set the ac on auto and got a reading of 45 deg up to 55.
the gf said it was cold but i didnt think it was.

i know the ac radiator is clean because i take the grill off a couple times a year and spray it out. plus i have some bug screen in front of it.

if i bought one of those recharge bottles with the gauge on them would that work well enough to see what psi i am running with?

They sell a cheap hose with a guage. Believe you'll be putiing freon in when ya hook a can with a guage.

ok so i went to walmart and got one of those bottles with the hose and gauge.

with the truck running and on max cool the gauge read 53. which is in the yellow (alert)
the compressor was running but the clutch on the front would not disengage. only when you turned the ac off would it stop spinning. i even high idled the truck and it still did not stop spinning. i watched it for a few mins both times.

any ideas?

ok so i went to walmart and got one of those bottles with the hose and gauge.

with the truck running and on max cool the gauge read 53. which is in the yellow (alert)
the compressor was running but the clutch on the front would not disengage. only when you turned the ac off would it stop spinning. i even high idled the truck and it still did not stop spinning. i watched it for a few mins both times.

any ideas?

It is normal for a compressor to remain engaged all the time WHILE the AC is selected and the truck is idling.

ok but how about the pressure reading?

bump

my truck and my grandpas truck were both work trucks for PPC an A/C and HVAC service.. the guys tweaked around with the a/c and they both get freezing... my grandpa would say the pump would freeze, but i dont know how much honesty is in that cuz i never took a look but it would be down to 39 recorded. almost unbearable.

well my only input would be changing the cabin filters but im pretty sure that the 03's dont got em.

With full gauges the readings should be no more that 70 on the low side. and around 210 on the high side. To much freon is just as bad as to little. The a/c should cool to a temp of around 46 degrees. Running the a/c on medium high for a short time before turning it to high help. It lets the coil cool down before the air passing over it tries to warm it up. On average on short trips under 50 miles. The factory a/c will only drop the ambient Cabin temperature 15 degrees. Of course it also depends how many cubic feet you have in your cabin. Also it is best to not use the max or recycle setting to start off with. the fresh air setting will draw in the outside air which is typically cooler that that which is in the cab on a nice summer day. Once the cab has cooled some the the max setting is more efficent. 134A doesn't cool as well at idle like the old R12. Once the rpm's get above 1500 it is better.

thanks guys. so with my reading of 53 on the low side is that bad? it was in the yellow on the gauge? there was 2 ports to check that i could find. both were next to the canister but the one was too big for my gauge to fit on. so i used the only one it would fit.

That reading is fine for the low side. If you are driving in 94 degree ambiant temperature, your maximum duct outlet temperature should be no more that 66 degrees ( low humidity) and 73 degrees(high humidity). this is the gm spec for the 6.6 so your temperatures of 45-55 are well under the max. This leads me to belive your a/c system is operating correclty. if you must have it colder, try the bypass trick.

Alright, let me get this out of the way. All of this is learned from the school of hard knocks (and no money).


On all my R-134a systems with an oriface system, the high side number is not as critical as the low side number.

The lower the low side number, the colder the system (to a point, as the low side switch typically cuts the compressor off under 25psi.)

You reading of 53psi on the low side (the only one you can connect to) indicates to me that the amount of freon in the system is wrong. If it's 53 at idle and the number slumps at, say 1500 rpm, down to, say 45, then, i believe it is truly overcharged. EVERY one I've touched works best at 30-35 psi at idle for a starting point, then confirm that 1500-2000 rpm does not allow the low side psi to drop enough to cutoff the compressor (25psi).

An undercharged system is always accompanied by excessive compressor cycling (or no compressor engagement at all) as the low side switch is opened every time it drops below 25psi.

Now, again in layman's terms, overcharging with r134a is a result of "wet" charging the system, IMHO. Instead of drawing in the r-134 as a gas (the slow way), real shops feed it in liquid form. IMHO, the expansion rate of the r134 thru the system is not constant. Any system I've "wet" charged will have different numbers the next day (and not always in my favor.)

Now, if any one here disagrees with any of the above, PLEASE share with me, as that's the only way I learn.

thanks guys. so with my reading of 53 on the low side is that bad? it was in the yellow on the gauge? there was 2 ports to check that i could find. both were next to the canister but the one was too big for my gauge to fit on. so i used the only one it would fit.

Yes the 2 Schrader fittings are different sizes. It’s about the only thing that is idiot proofed. It depends on whether or not the engine was running with the a/c on when you checked it. The system must be operating to be pressurized. I would say that your 53 psi reading is a little low under the load, but it is not bad (going to hurt). Try putting a little freon in and see if it cools the a/c. A thermometer is almost required to see a change in the temp. the system must (should be running) to suck in the freon easily. Read the instructions on the can so that you are putting the liquid in and not just the gas. Some cans must be inverted to remove the liquid. Again don’t exceed 70 psi on the low side.

Yes the 2 Schrader fittings are different sizes. It’s about the only thing that is idiot proofed. It depends on whether or not the engine was running with the a/c on when you checked it. The system must be operating to be pressurized. I would say that your 53 psi reading is a little low under the load, but it is not bad (going to hurt). Try putting a little freon in and see if it cools the a/c. A thermometer is almost required to see a change in the temp. the system must (should be running) to suck in the freon easily. Read the instructions on the can so that you are putting the liquid in and not just the gas. Some cans must be inverted to remove the liquid. Again don’t exceed 70 psi on the low side.


ok to answer your question. yes teh truck was running and yes the ac was on max when i took that reading.

Alright, let me get this out of the way. All of this is learned from the school of hard knocks (and no money).


On all my R-134a systems with an oriface system, the high side number is not as critical as the low side number.

The lower the low side number, the colder the system (to a point, as the low side switch typically cuts the compressor off under 25psi.)

You reading of 53psi on the low side (the only one you can connect to) indicates to me that the amount of freon in the system is wrong. If it's 53 at idle and the number slumps at, say 1500 rpm, down to, say 45, then, i believe it is truly overcharged. EVERY one I've touched works best at 30-35 psi at idle for a starting point, then confirm that 1500-2000 rpm does not allow the low side psi to drop enough to cutoff the compressor (25psi).

An undercharged system is always accompanied by excessive compressor cycling (or no compressor engagement at all) as the low side switch is opened every time it drops below 25psi.

Now, again in layman's terms, overcharging with r134a is a result of "wet" charging the system, IMHO. Instead of drawing in the r-134 as a gas (the slow way), real shops feed it in liquid form. IMHO, the expansion rate of the r134 thru the system is not constant. Any system I've "wet" charged will have different numbers the next day (and not always in my favor.)

Now, if any one here disagrees with any of the above, PLEASE share with me, as that's the only way I learn.


now to comment on yours. ill have to go check the pressure reading while the truck is under load. now you said i might be over charged at 53 while the other guy commented i may be under charged at 53. im a little confused?

If I stop short while charging an AC system, revving the engine to, say 1500, the low side pressure (the side you have a gauge for) will drop below 25psi and disengage the compressor. So, if you are low on R134, elevating the engine idle will result in your gauge dropping. Regardless of the reading, the gauge should "lose" pressure as the RPMs rise. Not a lot, but it will drop 5-15psi.


If I overcharge a system (or CAT ships a $400,000 excavator with to much charge in it), the low side psi will be higher than 25-40psi, and it will not cool adequately.

Just for argument sake, is there any shop in your area with a full gauge set? A high side reading of over, say 250, would indicate too much charge also.

Your compressor is remaining engaged during all your testing, so I'm convinced it's not low on freon, AND your gauge indicates 53. If you were to remove freon from the system (I can't really say how to legally), and lower the system pressure, it would not be hard or expensive to add some back.

By chance, have you discussed this with the shop that had the system open? Maybe they could throw a gauge set on it?

An overcharged system is as inefficient as an undercharged system.

well i just checked it again and it read 57 ideling and the same while at 1500. i tried it numerous times with the same results. i unhooked the gauge and reinstalled it. made sure it was clean. etc.

the work was done at the dealership and i know if i took it back they would charge me again.

think im going to try and see if my buddy has an actual gauge set.

The low side pressure is not only dependant on the system charge. The temperature and humidity play a major role. your 53 at 90 degrees may very well be 40 psi at 70 degrees. from the general motors a/c system performance chart, your pressure and temperature were both in spec for the ambiant temperature you gave us. i would not try to remove any freon.

If I recall, my 03 had a problem with the coolness of the AC. There was a problem with the Crew Cab AC's. It had a different condenser or something in it. Im sure there is info on the site somewhere.
Andy

well i just checked it again and it read 57 ideling and the same while at 1500. i tried it numerous times with the same results. i unhooked the gauge and reinstalled it. made sure it was clean. etc.

the work was done at the dealership and i know if i took it back they would charge me again.

think im going to try and see if my buddy has an actual gauge set.

How long ago was the work done. if it was within a reason amount of time they sould look at it for free. I was in the conversion industry for many years and have done thousands of a/c installs mostly the additon of rear air units tapped into the factory system. both R12 units and 134A. you can get a inexpensive set of gauges from almost any parts store. I am also MACS certified

The Napa near one of my jobsites had a full gauge set, including the little can tap for $65. I woulda bought it instead of the ones i have.
Post #11 ^^^
How long ago was the work done. if it was within a reason amount of time they sould look at it for free. I was in the conversion industry for many years and have done thousands of a/c installs mostly the additon of rear air units tapped into the factory system. both R12 units and 134A. you can get a inexpensive set of gauges from almost any parts store. I am also MACS certified
Previously, you posted that 53 psi at idle was normal...Every machine or truck here with an oriface system comes out around 30-40 psi at idle, depending on ambient temp. With that said, Am I not correct in stating that the greater the charge amount, the higher the low side pressure, all other variables being the same???

With full gauges the readings should be no more that 70 on the low side. and around 210 on the high side. To much freon is just as bad as to little. The a/c should cool to a temp of around 46 degrees. Running the a/c on medium high for a short time before turning it to high help. It lets the coil cool down before the air passing over it tries to warm it up. On average on short trips under 50 miles. The factory a/c will only drop the ambient Cabin temperature 15 degrees. Of course it also depends how many cubic feet you have in your cabin. Also it is best to not use the max or recycle setting to start off with. the fresh air setting will draw in the outside air which is typically cooler that that which is in the cab on a nice summer day. Once the cab has cooled some the the max setting is more efficent. 134A doesn't cool as well at idle like the old R12. Once the rpm's get above 1500 it is better.

This was my original statement. All my a/c work has been done in texas were the temps are much higher and the humidity as well. have you tried to just put a little freon in and see wether or not it helps. with 134A you can always let a little out if it doesn't. If it goes in the wrong direction. Yes you are correct the greater the charge the higher the number on the low side and the high side as well. up in PA the low side may need to be around 40.

Just finished a '96 Peterbilt A/C system (all new components, I ain't never seen a system plugged like this: Auction truck I just got).

With the low side gauge hooked up, 30psi (at idle) gave the coldest temperature and as I overcharged it, the low side climbed to 50 and the interior duct temperature climbed. Reduced back to 30 at idle and it's like a meat locker in there. Throttled up and the low side drops below 25 (and compressor shuts off). Added enough to maintain 35psi at idle and back to meat locker again. Ambient 72deg F, interior air temp 42 deg F:D.

the service work was done under 2 years ago. when i get some more time im going to try and get some good gauges.

sorry tothemax and haymccall. my statement of 53 was incorrect. it has been a while since i have done an a/c repair. i have always used the high side number. haymccall you are correct with the lower number.