weird ac problem

[cbailey]

Hello everyone. I have a strange problem with my ac. I have a 07 chevy aveo and while the car is at idle the ac cools good, if you increase the rpm's it the air starts to turn warm and stopps cooling. I have checked everything that i know to check, the compressor does not stop, the clutch does not disengage, the fan comes on at the radiator when you cut the ac on. the only gauge i have is a cheap low pressure gauge and the pressure reads high on the low side idont know about the high side. I cannot find a strainer no where in the system and none of the parts stores list one. So i did find out that the system has a expansion valve and i was wondering if it could be hung open or closed to , if open wouldn't it be like an open coolant thermostat and not letting the freon stay in the evap long enough. All help i thank you for in advance. Almost forgot when ac stops cooling you can stop the car come to an idle cut the ac off and back on and it will start cooling again until you drive off.

[brcidd]

Comprerssor maybe destroking early due to mechanical destroker design- at high rpm they are designed to destroke so as not to over rev the compressor- but it is supposed to be at about 5000 rpm- yours may be going down at 2000 or so-- discharge pressure will confirm---report pressures please at varying rpms

[j cAT]

Originally Posted by cbailey

Hello everyone. I have a strange problem with my ac. I have a 07 chevy aveo and while the car is at idle the ac cools good, if you increase the rpm's it the air starts to turn warm and stopps cooling. I have checked everything that i know to check, the compressor does not stop, the clutch does not disengage, the fan comes on at the radiator when you cut the ac on. the only gauge i have is a cheap low pressure gauge and the pressure reads high on the low side idont know about the high side. I cannot find a strainer no where in the system and none of the parts stores list one. So i did find out that the system has a expansion valve and i was wondering if it could be hung open or closed to , if open wouldn't it be like an open coolant thermostat and not letting the freon stay in the evap long enough. All help i thank you for in advance. Almost forgot when ac stops cooling you can stop the car come to an idle cut the ac off and back on and it will start cooling again until you drive off.

you need to check the low high side pressures and report what found when at idle rpm and at the 2000 rpm.

could be air in the system. this would cause high pressures and erratic cooling.

[Tech II]

Feel the lowside line.....does it feel cold? Now increase the rpms's....does it still feel cold? Have someone inside the vehicle....is it cold air or warm?

[cbailey]

ok, i got a good set of gauges today after work and i will post what kind of pressures i find

[cbailey]

ok here it goes. while i was feeling good about working on the ac i put a expansion valve on it per other peoples thoughts. after, i could never get the pressures close to correct but one time. it was around 90 degrees outside so i had the low side on about 55 and the high on about250. cut ac off then back on and all pressures went way high and i mean high , evacuated some freon got the numbers back down but never could get them close.after that it was the same old same old cool at idle stop cooling at increased rpms. the numbers were idle 65 on low , 185 high, rev up to2000 numbers were 75 and 190 back and forth. ac will not cool after returning back to idle unless you cut it off and then back on. this is all new to me so now im lost

[cbailey]

p.s. i did pull a vacuum on the system before recharging (another new toy)

[cbailey]

update on my ac proplem. just installed a new compressor and dryer and as of now it cools like a charm, thanks everyone for the help

[j cAT]

Originally Posted by cbailey

update on my ac proplem. just installed a new compressor and dryer and as of now it cools like a charm, thanks everyone for the help

I missed your later postings with your findings. with what pressures you got I would say the compressor valves failed. too much refrigerant can do this. or installing the refrigerant on the low side with liquid instead of gas damaged the valves. if the charging can is inverted liquid will enter the compressor and can/will damage the valves.

when the low side pressure is high and the high side too low the compressor is not pumping correctly .

one thing about these systems , is if you start to get to the point of adding too much refrigerant , the high side will rapidly increase.