04 AC Blows Warm

gerg001 · 07-07-2016, 07:43 PM

Need help with testing a 3 wire ac pressure switch 2004 Sunfire ac clutch is not engaging. I tried to add freon but the gauge that came with the refrigerant says 40 psi so that shouldn't be it. Jumped the clutch relay and the compressor engages. So based on the attached wire diagram, the only thing left seems to be the pressure switch. Its a 3 wire switch. How do you verify this type of switch is working? Any help would be appreciated.

brcidd · 07-07-2016, 09:22 PM

Was the compressor running when you saw the 40 psi? If not, then 40 psi is your static pressure (compressor not engaged) and your system needs 47 psi to turn on the compressor. So if 40psi is without compressor running, then you are extremely low on refrigerant and compressor will come on once pressure rises above 47 psi as you add refrigerant.

If above is the case, then your pressure transducer is protecting the compressor by disabling it, the last thing you want is the compressor to run with little or no refrigerant which carries the oil needed to lubricate the compressor.

gerg001 · 07-07-2016, 10:25 PM

The compressor was not running when I measured 40 psi. So if 25 psi is not the right number for compressor OFF then I will add more refrigerant tomorrow. Thanks for the tip!!! That will be easy if that's the case.

Another question... I have read online on some forums that the compressor has to be running to add freon. But then you aren't suppose to run the compressor if the freon is low. These rules seem to be conflicting. What is correct?

brcidd · 07-08-2016, 07:27 AM

Let's think about it---your car has 25 psi in system--- your can from parts store has 80-90 psi in it-- you attach it to low side port on system- can is warm and 80 psi will push into 25 psi system until it equalizes at about 70 psi--so halfway into the flow of refrigerant the compressor will kick on automatically (when system pressure hits 47 psi). It may take 5 minutes- but so what....

Remember- that the red yellow green on the gauge only apply when compressor is running......

Now think again--- your system has leaked 97% of its refrigerant (25 psi static tells me that). If this was a tire- and you fixed it by "adding air" - you would soon go flat again, and you would say it was "not fixed". So same applies to a/c system- just because you added refrigerant, it will soon "go flat" again- because you have not found and fixed your leak.

Big hint- look at the compressor body- they tend to leak on compressor belly.

If you still want pin-outs of pressure transducer- I have them...

Tech II · 07-08-2016, 10:08 AM

brcidd gave you good info......

This system is different from old systems, which used a pressure cycling switch....on those systems, the compressor would cycle when limits were reached....

The system you have does not cycle, since the stroke of the compressor can be changed, to keep pressures within limits....thus it runs constantly....

With the old system you could jumper the pressure cycling switch.....you can't do that with a pressure sensor.....

So, as brcidd states, just attaching the can will raise the static pressure enough for the pressure sensor to send a valid signal to the PCM, to engage the clutch....and as he stated, your A/C may work for a long time, or it may work for a day, depending on how bad the leak is....

gerg001 · 07-08-2016, 06:59 PM

I put about 14 oz of freon in it. The running pressure is about 50 psi and the OAT was about 90F. The compressor started running after putting about 2 - 4 oz in... Yeah!! though I had a bigger problem. Thanks for the help. It blows cool but not cold. I noticed the high pressure line started sweating and the low side at the firewall was cool but no condensation with 50% RH outside. I didn't have a way to measure the temp at the outlets but it seemed not as cold as it should be. Neither the high or low side lines have insulation on them. Should I add some?

brcidd · 07-08-2016, 08:48 PM

Put more in it- according to underhood label- 14 oz is not enough!

gerg001 · 07-09-2016, 06:57 AM

OK I will. I was going by pressure rather than total weight added because it wasn't empty when I started.

Tech II · 07-09-2016, 08:01 AM

Problem is, if you add a lot of refrigerant to a system, because of a leak, that means you can have air in the system......with air in the system that takes up space in the system, and you not get the same amount of cooling.....

You would need to find the leak, fix it, EVACUATE THE SYSTEM, add oil if necessary(especially if there was a leak), and then add the proper amount of refrig by WEIGHT....

gerg001 · 07-09-2016, 07:55 PM

I was hoping for a slow leak where the refrigerant would last the season but when I went to add the additional can of refrigerant as suggested, the system was already discharged again (only one day). So no such luck. Need to find the leak. I don't see any obvious signs of oil on the lines or on the compressor. Thinking about buying a sniffer. Any suggestions??

brcidd · 07-09-2016, 09:35 PM

Your Cavalier has dye in it from the factory- so buy the UV glasses and blacklght kit from autozone and wait until dark out and look at all the a/c components. The leak will jump out at you as a bright green residue. Much cheaper (about $ 14) then the sniffer...

Tech II · 07-09-2016, 10:15 PM

Also check the hi and lo side valves, they are known to leak.......

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