A/C issues

[blazinlow89]

My truck is approaching 120k miles and with the heat setting in quickly I would like to get the A/C working.

First the issues, the A/C compressor will kick on and off intermittently about 10 seconds off, 5 seconds on. I was having issues with the engine rpm bouncing around when it was turned on, but I cleaned the throttle body today and that issue is gone, runs nice and smooth with the A/C on. I checked the pressure in the LP side, and it fluctuates with the compressor, when off it sits around 65-70 PSI. When the compressor turns on the gauge needle swings down to around 10-20 PSI, the pressure then sweeps back up until the compressor turns off. The HP line gets cool, but not cold. The accumulator stays warm though.

Another random thing is that with it on the passenger in the cabin feels about 15 degrees colder than the drivers side. I have the LS with the manual climate controls. I have not recharged it as the 70 PSI was on the caution area of the gauge. I do not have a HP gauge.

Do I have a bad LP switch, is the accumulator bad, or am I going to have to suck it up and go for a new compressor.

 

[BRomanJr]

My truck is approaching 120k miles and with the heat setting in quickly I would like to get the A/C working.

First the issues, the A/C compressor will kick on and off intermittently about 10 seconds off, 5 seconds on. I was having issues with the engine rpm bouncing around when it was turned on, but I cleaned the throttle body today and that issue is gone, runs nice and smooth with the A/C on. I checked the pressure in the LP side, and it fluctuates with the compressor, when off it sits around 65-70 PSI. When the compressor turns on the gauge needle swings down to around 10-20 PSI, the pressure then sweeps back up until the compressor turns off. The HP line gets cool, but not cold. The accumulator stays warm though.

Another random thing is that with it on the passenger in the cabin feels about 15 degrees colder than the drivers side. I have the LS with the manual climate controls. I have not recharged it as the 70 PSI was on the caution area of the gauge. I do not have a HP gauge.

Do I have a bad LP switch, is the accumulator bad, or am I going to have to suck it up and go for a new compressor.

From the sounds of it, you are low on freon. The yellow and red areas on the LP gauge is only relevant when the compressor is running.
When freon is low you will also get warmer air on the drivers side of a dual zone system (Manual or Auto).
The quick cycle is also a sign of low freon.

It is unlikely that you have air in the system so adding freon/refilling should fix it, until it leaks out again.
With only a LP gauge, it is difficult to get it filled accurately, If the leak is large, you should get it fixed and filled properly.

 

[TollKeeper]

What he said is dead on.

 

[blazinlow89]

Ok I serviced it last night. Just a can of freon. I have done it before on other vehicles, and I have a vacuum/leak tester at my disposal if need be.

The gauge I was using came with a can of freon we used to my brothers scoobie. At idle no AC on it was at 75 PSI red zone on the gauge. With the AC on it would drop down in a sweeping motion to as low as 5psi. I serviced it slowly while it was running, the gauge started going down each time. Now at idle no ac I am at 65 (yellow zone). With AC on, which by the way it stays on now while running no more off, on, off, on every 5-10 seconds. At idle though it is at 27-32 psi. It was at 35 when I first started watching it. I attribute this to the system circulating the freon into the system completely.

Now accumulator and the line crossing the engine have condensation, and the air blows cold. I am going to monitor it to see what happens, I sprayed soap water on the hoses and connections i could see with no leaking obvious. The compressor is the same way. Does anyone know the service requirements for our AC system, what is the proper operating range?

I might have a hidden leak somewhere, but I know everything works so I am happy it will not cost me a compressor, condenser or accumulator .

 

[The_Roadie]

The chart is very complex, but let's get some middle of the road numbers. For a SWB, not an EXT:
Ambient temp 76-85 degrees F, 35-50% relative humidity. Low side 31-42 PSI. High side 160-200 PSI. Max center dash outlet air temp 57 degrees F.

 

[blazinlow89]

The chart is very complex, but let's get some middle of the road numbers. For a SWB, not an EXT:
Ambient temp 76-85 degrees F, 35-50% relative humidity. Low side 31-42 PSI. High side 160-200 PSI. Max center dash outlet air temp 57 degrees F.

I seen a few sets of gauges that had the temp range on them, when I was getting my freon. I did test the high side which is at 145PSI. It is only about 60* right now so the low numbers might be accurate. It is supposed to be 72 tomorrow so I will check again. So I am assuming at around 70* i should be at around 35-37 PSI. I will check tomorrow then when it stops raining.

I am just glad I got the windshield to condensate while it was running. I assume that most AC systems have a slight leak naturally and around the end of last summer it was not as cold as usual. Being 8 years old I am sure has something to do with it.

 

[Taz6056]

Not to Hijack... but Roadie could you possibly post the numbers for the EXT/Longwheel base models? Does model matter? I mean are the numbers for a Trailblazer EXT and my Envoy XL the same?

Marc.