No A/C all of a sudden. Compressor is working..what now?

[Caddynut]

Sorry in advance of the lllooonnngg post, but I wanted to be thorough. I have never had any problems on my 2001 STS with the air conditioning, but the other day I drove about 50 miles and the a/c worked perfect. I parked for about 2 hours in a parking garage, came out and went on my way. The passenger's side was a little cool, but the drivers side was all hot air no matter where I put the temperature. I checked the compressor and it is cycling just as it should. the R134 level is good and the low pressure line going into the firewall is ice cold. I removed the glove box in hopes of finding that the air door actuator wasn't moving. The door over the fan opens and closes as it should and the one in the center moves. The vents switch from defrost, vents and floor as they should. What else should I look for now? Could it be an air blend door and where would that be located. Thanks.

[Logan]

Try adding a can of freon.

It's a classic known quirk on these cars....cool passenger side...warm drivers side.

AC gauges will show 'normal' pressures and no 'low freon' codes or panel messages will appear or set.

The system is low on freon.

You can get a can of 134a at Big Lots for $7.

[rockfangd]

How do you know the freon is not low? that would be my first suspect for the problem you describe.

Charge should be 2.0 lbs r134a.

low side pressure should be between 30 and 40,

high side should be 1.5 times the outside ambient temperature.

Example, its 80* outside. which means high side pressure should be 200

[rockfangd]

lol you beat me. I type too slow

[Caddynut]

I added a can of R-134 and no change at all. I will hook my good pressure guages up tonight and see what the pressure is at. One of the el cheapo guages said it was in the normal level. Both passengers and drivers sides are warm, but it does change to heat when you crank up the dial.

[winterset]

Try turning the controls back and forth to the max/min to see if it re-calibrates the actuators. Max hot to max cold, defrost to heat, etc. do it a few times.

[KHE]

Feel the evaporator inlet and outlet lines - they should be the same temperature. If the outlet is warmer than the inlet, the system is low on refrigerant.

[Caddynut]

I tested the low side of the system and it was right on the money at 34 pounds with the compressor running. The car did take about 6 oz. of R134, but it didn't make any difference. Compressor was cycling normal. Both lines out of the evaporator are equal temperature and the low pressure line gets ice cold starting about 6 inches from the evaporator towards the firewall. I have turned both the passenger and driver control anywhere from 60-90 degrees. At 90, both sides roast you out of the car and drop in temperature when the control is lowered. when I turn the passengers side to 60 it gets sort of cool and the drivers side gets down whatever the outside temperature is. Not anywhere near cold. I know that usually when there is a difference in temperature between the passengers and drivers side, there is a low refrigerant problem, but I am pretty convinced it is something else. I appreciate all of your suggestions as it is helping me to eliminate the options and hopefully narrow down the problem. I can tell you one thing...I sure do miss the "old school" basic control cables that just move an air temperature door.

[rockfangd]

maybe a stupid question but does your ambient temp readout accurate?

not sure if it is tied in with the system or not

[Caddynut]

Good question. I honestly haven't looked at that in awhile. I will check that when I get home from work. I guess my next step is to try and find the drivers air temperature door and see if it is working. I have checked the passengers and it moves like it should

[Caddynut]

ambient temp is normal.

[rockfangd]

ok See if there are any codes via the onboard diagnostics.

A quick search in the forum will explain how.

Post what you have here.

[Cadillac Jim]

The link in my signature block goes to a Caddinfo "how-to" page on reading your codes.

[Caddynut]

stupid me, I did forget to mention I had pulled the codes. I had several, but none were related to air temp door malfunction or the hvac system. I do have a problem with my main harness connections (after I had head gaskets installed). I have the list at home and will post the results after work.

[Caddynut]

Ok. I pulled the codes

U1000

P0481

P1571

P1041

C0594

C0710

U1040

Like I said before, I know I have harness problem and I suspect some of the pins are not connecting in the plug.

[Cadillac Jim]

U1000 Class 2 Communication Malfunction
P0481 Cooling Fan Relay 2 Control Circuit
P1571 Traction Control Torque Request Circuit
P1041 [Possibly O2 Heater Circuit Malfunction (Bank 1, Sensor 2), possibly a fuel injector code; check this for an error as it does not seem to be a GM code]
C0594 Right Rear Solenoid Circuit Open
C0710 Steering Position Signal Malfunction
U1040 Loss of Class 2 Communications with ABS

The P0481 could be causing the A/C to hold back a bit because the cooling fans are not working properly.

[Caddynut]

Thanks Jim for the info. I will fix that right away and see if that makes a difference.

[Cadillac Jim]

Be sure and check to see if the P1041 is the right code. I don't find that as a code on any GM car.

[airmike]

i suspect that is a p0141

[Cadillac Jim]

If so, then

P0141 Heated Oxygen Sensor (HO2S) Heater Performance Bank 1 Sensor 2

This is a tired cat. Could be cracked or clogged, or on the way to being clogged.

[Caddynut]

I will check that out. I hope not, but could be. more problems.

[Cadillac Jim]

Re-check the code first. Whatever the P1041 turns out to be, post it here.

[Caddynut]

well, I have an upsetting update. Yesterday, I rechecked the R134 low side pressure and, again, it was right on the money, BUT, at about 2000RPM, the compressor sounded like it had a rattle to it. I shut the car down for the night. Today, the compressor won't even kick on. I guess the compressor crapped out on me.

[Cadillac Jim]

You may have overfilled the Freon. Reset the codes and try again. If that lets the compressor restart, then use the gauges again, this time watching the pressure as you slowly rev the engine. Let out a little Freon if necessary.

Other things that can cause similar problems are a clogged dryer/accumulator and a clogged expansion orifice.

Environmental regulations may be a point to note. Your local regulations may require a Freon recovery system to bleed off Freon.

[barczy01]

The compressor is toast. I have seen a couple this Summer so far. The suction side of the compressor is no doing its job.