Automotive Air Conditioning Information Forum (Archives)

Provided by

We've updated our forums!
Click here to visit the new forum

Archive Home

Search Auto AC Forum Archives

AC Cycling

u118224 on Mon May 24, 2010 10:43 AM User is offline

Year: 2002
Make: Chevy
Model: Cavalier
Engine Size: 2.2 OHV
Refrigerant Type: Unknown
Ambient Temp: 85
Pressure Low: Unknown
Pressure High: Unknown

This is my daughter's car. The car has had AC problems for a few years but now she wants it fixed. First off, a friend of mine does home AC and he checked the system last year. No additional refrigerant was needed, but I didn't ask him what the pressures were. The compressor cycles on and off rapidly; there is cold air but then it blows hot. Since both the clutch and compressor work, I assume the problem is elsewhere.

I'll catch up with my friend and get low and high side readings while it's cycling. What other info is needed?

Thank you.

MBDiagMan on Mon May 24, 2010 10:49 AM User is offline

Short cycling as you describe typically indicates a low charge.

Have a great day,
ASE Master

u118224 on Mon May 24, 2010 11:09 AM User is offline

Thanks for the reply. I'll have him check the refrigerant again and provide pressure readings.

HVargas on Mon May 24, 2010 11:13 AM User is offlineView users profile

Just checking pressure alone is a good way to ensure the system had refrigerant and to test that the pressure switches are working, but in order to check the amount in the system, you need to have it professionally evacuated so they can tell you exactly how much was recovered.


When considering your next auto A/C purchase, please consider the site that supports you:
Contact: Arizona Mobile Air

u118224 on Mon May 24, 2010 11:27 AM User is offline

Thank you Adam. Can you tell me how much refrigerant the 2002 Cavalier system holds, or should I check with the dealer?

HVargas on Mon May 24, 2010 2:12 PM User is offlineView users profile

There should be a service label under the hood but it takes 1.5lbs or 24oz.


When considering your next auto A/C purchase, please consider the site that supports you:
Contact: Arizona Mobile Air

u118224 on Tue May 25, 2010 1:37 PM User is offline

I'm going to have the system evacuated and recharged Thursday night, but here's an update. My daughter dropped the car off so I could drive it home. Ambient temp was high 80s and high humidity. While driving, the air would cycle, but it was mostly warm. When I got home I left the AC running and popped the hood. The engine cooling fan (electric) was not running and the AC compressor did not run or even cycle. The cooling fan finally came on, probably for high water temps. While the cooling fan was running, the AC compressor cycled as follows, it would be on for 1 second and off for 6-10 seconds. I shut the car off and restarted it after it had fully cooled. With a cold engine, the cooling fan ran and so did the AC compressor, it ran constant with no cycling and blew cold air. After 5 minutes, I shut the car off.

It seems to me that the cooling fan should have been running when the car was hot and idling with the AC on. My question is, is there a pressure switch on the high side that triggers the cooling fan, or should the fan run whenever the AC is on? Lastly, where's the best place (other than the dealer) to get a schematic of the AC system. Thank you.

k5guy on Tue May 25, 2010 4:36 PM User is offline

Yes there is high pressure switch. That is why we need pressures to help diagnose. It might be a bad switch but a high and low pressure reading can help isolate what is wrong.


Send me e-mail

Chick on Tue May 25, 2010 6:32 PM User is offlineView users profile

Have the system evacuated and recharge properly..then check for leaks, the fan comes on with engine heat, and also when the compressor runs, low charge will cause both to cycle on and off...

Email: Chick


Freedoms just another word for nothing left to lose

u118224 on Thu June 03, 2010 5:09 PM User is offline

Here's an update, and thanks to everyone for the assistance. We checked the car last week, with these results. The static low side pressure was 90-95. We pulled the pressure switch connector to see if we could jump the connection to start the fan; that didn't work, probably 'cause the car wasn't running. We reconnected the switch and restated the warm car. The compressor and cooling fan both ran, no cycling at all. The low side pressure with the AC on full was 35. My friend didn't see the necessity of recovering the system (he's not an auto tech) so we didn't do that. He felt the metal line by the dryer with the AC on and said it was cooling in the mid 30 degree range. Anyway, daughter says the AC works great now. The only possibility is that the pressure switch connection was faulty.

GM Tech on Thu June 03, 2010 6:35 PM User is offline

You need to know that you have a variable stroke compressor-- that does not cycle by design to avert freeze-up--if it is cycling- it has to be high pressure cut-outs- these systems never cycle for low charge- as you do not have a fixed displacement compressor.

Also that "switch" you tried to jump is a 3 wire transducer- do not try to jump it-- it can mess up your ecm. Your problem is air flow across the condenser- due to most likely an inop fan- test your fans- test the fan relays.

The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

Back to Automotive Air Conditioning Forum

We've updated our forums!
Click here to visit the new forum

Archive Home

Copyright © 2016 Arizona Mobile Air Inc.