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AC questions and opinions

not sure. I think it's been over a year since I bought and installed it. I will have to look for the paperwork and see if it was lifetime or 1 year. I noticed that grime accumulation yesterday. that might me my leak! need to find my UV light and see if it glows. one of the reasons I don't care for these pancake compressors!
 
dbrannon79 said:
@WarWagon what's your thoughts on the pressure readings? it cooling good now, and my trip to work this morning it got down to 40 but it was about 76 outside this morning.
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1200 RPM The evaporator is near the cut out temperature of 32F. What is the actual condenser temperature: does it agree with the gauge reading?

I am used to 300 PSIG on the high side, condenser temp of 160F, in 105F+ outside temps as R134A gives it up with the R4 at idle RPM.

Looks like you got a fan system that makes a difference in A/C performance. Have you moved the hot engine/trans oil cooler behind the condenser? https://www.thetruckstop.us/forum/t...condenser-and-radiator-and-add-aux-fan.47322/

Any fresh oil on the compressor body o ring area? The four bolts on the compressor itself: that area alone has also leaked on me.
 
I have to find my inferred temp gun, my father n law was playing with it and now I can't find it! as soon as I do, Ill get the condenser temps.

there is a light coat if dirt / dust that's on the body of the compressor that looks like oil may be seeping out of the body. I will clean that off and monitor it.

No I haven't moved the trans cooler behind the condenser yet. I had planned to but was wanting to use the factory cooler. that idea failed so I will have to order an aftermarket cooler and do this one if these days.


my trip home yesterday it performed very well. leaving the parking lot and driving 10-15 mph though the plant to the entrance about 1/2 mile or so, it had already cooled down to 50 before I got the the front gate! that was a big difference. Never felt it cycle the whole trip home. but it did cycle on and off again this morning heading back to work which is a given since it's much cooler in the wee morning hours. I think it's performing well at the moment, maybe with looking at the pressures getting a bit low for the outside temps. if the condenser temp agrees with the pressure, maybe increasing the charge from 36 oz to a total of 40 oz might be the ticket.
 
Once I do figure out the exact charge amount I will make myself a label using the circut machine and stick it somewhere under the hood were it doesn't get removed with a replaced part like GM did. that is if I can't order the factory one it had!
 
There should be website who specify how much refrigerant is needed.

As for the low pressure switch, I am not sure if they are even ACDelco anymore.
I think the brand is Four Seasons who are the makers of AC components for this truck.

IMO, in TX, it is probably worth having a good AC Shop do the installation or even evacuate-recharge.
This truck took a lot of refrigerant and the Suburban used even more.
The challenge with cans is that you will loose some every time you hook a new can and unhook the old one.
I paid around $1000 15 years ago.

I think if you need a new compressor, that is when you can retrofit the Sanden.
IIRC, from Thefermenator post, Sanden compressor needs less refrigerant.
 
JMJNet said:
There should be website who specify how much refrigerant is needed.

As for the low pressure switch, I am not sure if they are even ACDelco anymore.
I think the brand is Four Seasons who are the makers of AC components for this truck.

IMO, in TX, it is probably worth having a good AC Shop do the installation or even evacuate-recharge.
This truck took a lot of refrigerant and the Suburban used even more.
The challenge with cans is that you will loose some every time you hook a new can and unhook the old one.
I paid around $1000 15 years ago.

I think if you need a new compressor, that is when you can retrofit the Sanden.
IIRC, from Thefermenator post, Sanden compressor needs less refrigerant.
Click to expand...
There is, it shows 36 oz for the crew cab. but for what ever reason ever since I have been able to get the AC working it has always has what seemed to be low pressures on both the low and hi sides compared to temps. that's what has me scratching my head, something isn't jiving. and without a way to weigh the amount going in I'm shooting in the dark relying on what the can volume is. every other vehicle I have done in the past I have never had this much issue with as far as the pressures to temp are concerned. not to mention the R4 is very temperamental with a low charge and oil starvation!!!
 
I really feel like GM goofed with using the same size orifice tube for these trucks across the board wether older using old R12 or the 93+ using R143A. I am leaning towards the possibility it needs a smaller orifice size and the engineers were too lazy to make one when they changed to R134A.

If you look up the orifice tube for an early 90's model it shows the same one as the late 90's does. to me that doesn't make any sense!
 
dbrannon79 said:
if the condenser temp agrees with the pressure, maybe increasing the charge from 36 oz to a total of 40 oz might be the ticket.
Click to expand...

I would not experiment with a system showing signs of a leak and say the numbers are final. Without recovery equipment telling you (recovery accuracy runs 1/4 LB low on mine) what was in the system it's a WAG how fast it's leaking out and thus how much is left in the system. The last 1.19LB system I did was low, but, lost in the accuracy limits of my machine.

dbrannon79 said:
If you look up the orifice tube for an early 90's model it shows the same one as the late 90's does. to me that doesn't make any sense!
Click to expand...


The freeway speed with high compressor RPM and high MPH airflow over the condenser is where the OT's are sized. This Obsolete poor performing technology, but used because it's CHEAP, is why the VOV was invented. You trade idle performance with OT sizes at the risk of higher head pressures at freeway speed.
 
I finally found my temp gun, shot the condenser in several places through the grille but the highest temp I saw was around 126. ac seems to be cooling good so far other than the recirc door.

the recirc motor has been out for a while and I had the door propped up so it wouldn't draw in any outside air. I got a wild hair and was able to pull the motor out and did a repair on it. had another motor that had a different connector but internally they were the same. swapped out the broken gear and re-installed. it seemed to work great for a couple of days and then decided to not want to close, keeping outside air into the cab!

I couldn't figure out why, every time I went to mess with it, it would close and work just fine, then go for a drive. next time I started out somewhere it would open and stay open. I finally got fed up with it and decided to disconnect the pressure sensor on the condenser, now it seems to close and open with the dash button flawlessly! mind you the ac pressures were not high enough to trigger the sensor because the fans were still cycling on and off when driving slow. I figure that sensor is bad. do I really need it? my thinking is when the door opens and draws in outside hot air, that would make the pressures increase along with less cooling in the cab. Not to mention the first time it opened I heard the sound of leaves in the blender lol. Ima gonna have to pull the blower back out and clean that up again!
 
I had something odd happen today while driving home from work. left work and turned the blower up on high to cool the cab down. after a few seconds chunks of leaves shot out of the drivers side vent!! this got me to thinking how on earth could those large chunks of leaves that the blower sucked in get past the evaporator and make it through the duct work out the vents? the only thing I can think of is there must be a large enough gap around the evap and the air box housing to allow this to happen. would this indicate a problem where air from the blower is pushing around the evap core and not going though it? I know there seems to have been an issue in the past for the heater core where bypassing it seemed to make the ac colder.

I have another air box in the garage to replace mine whenever I get around to doing the dash and interior. I might need to open it up and study how the air flows through it. already plan to pull the plastic around the wipers and put some fine mesh like window screen under it to keep the crud from getting in there at some point.
 
That’s gonna be next on my to do list! Did a few errands around town today and I see my recirculate door is back to randomly opening and closing again even though I disconnected the sensor on the condenser! Started playing with the buttons and knobs on the control and it went back to working. Later this afternoon it starts acting up once again!! This thing is gonna drive me nuts lol. Can a bad ac control do this? My last trip into town I weaseled my hand in where the CD player was and fiddled with the wires and it went back to working and then just quit all together! Stuck open sucking outside air in the cab! :banghead:
 
dbrannon79 said:
I see my recirculate door is back to randomly opening and closing again
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Only because it's a real PIA to get the screws out: the recirculate door motor itself is the problem. Either it's a broken gear, broken gear slipping on the shaft, or one of the pots in the board is going bad. Our 1995 Yukon would have the door flop open at freeway speed and re-close slowing down. I could push it open with my hand. The motor was running like crazy trying to close it but the gear was just slipping on the shaft.
 
WarWagon said:
Only because it's a real PIA to get the screws out: the recirculate door motor itself is the problem. Either it's a broken gear, broken gear slipping on the shaft, or one of the pots in the board is going bad. Our 1995 Yukon would have the door flop open at freeway speed and re-close slowing down. I could push it open with my hand. The motor was running like crazy trying to close it but the gear was just slipping on the shaft.
Click to expand...
I had pulled it the other day and swapped the big gear out inside. but didn't think about the circuitry. It worked when I tested after doing that. maybe with this heat (106 yesterday) it's going funky. I was curious if the control board that's in behind the knobs in the dash could do this. back when I first got the ac working, I had to pull it and do a hill billy repair due to the ac push button switch not activating the compressor. plus glue the blower switch on after all the attachments were broken off! I wasn't going to spend $100 on that thing lol

I wonder if I can find someone with a parts truck that has a good one in it!!
 
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