AC problems! :S

[iaoun]

hi guys ,


i drive a lumina ss 07 ( similar to the pontiac g8 gt ) * L98 engine*
i ve been surfing with my AC , last week i was rolling at 120 km/h then ive kicked it to reach 180 km/h , then i heard something broke, unfortunatly it was the ac kompressor,

i had a deal with a mecanic and he replaced it for me , including a full system flushing , we have changed the driyer and the valve too ...

what happens now is that whenever i switch on the ac ,, ( this happens at night , when the temprature is low , because i live in a very high tempered country )
it runs perfectly till it reach the temp it supposed to reach, then the compressor goes off , and whenever the temp varies it supposed to go on again, yet its not, what is actually happening its that the compressor is never going on again, so id have to switch off the ac button, the turn it back on ... and so on !


expecting the experts replies! ..

thanks

[MIEngineer]

I would check the wiring connectors at the compressor assembly to the harness.

Otherwise, is there enough R134a (refrigerant substance) in the system?

[GRRRR8]

My experience says it could be a incorrect R134A level. If the level is low it will turn the a/c off as the pressures are low at cooler temps. If it seems to work fine in the daytime, high probability this will be your issue.

Make sure the freon is charged with a machine that weighs it. A few ounces off is all it will take to cause this issue.

[MIEngineer]

^ Yep...ran into this more than once when I worked at a supplier for HVAC..hence my second line :)

[iaoun]

just to double check R134A is the freon ?

thanks for the support !

[WickedMom]

Do our cars have a cycle switch like on the old GM trucks?

[iaoun]

Do our cars have a cycle switch like on the old GM trucks?


no idea ... do you have any picture of that ?

[WickedMom]

I don't think our cars have one.. It was just thought since it doesnt cycle back on after reaching temp.

[TomPierce]

I believe our compressors don't switch off and on like older compressors do, but instead they are variable displacement compressors which change the volume of refrigerant which is compressed depending upon demand.

Don't know why it would work then fail, though.

[-Ray-]

I believe our compressors don't switch off and on like older compressors do, but instead they are variable displacement compressors which change the volume of refrigerant which is compressed depending upon demand.

Don't know why it would work then fail, though.

I didn't see what kind of compressor is installed.

[LDM]

I didn't see what kind of compressor is installed.

Compressor Specifications:
http://forum.grrrr8.net/attachment.php?attachmentid=15322&d=1338219520

So yes, they don't cycle with a clutch like older compressors do.

[WickedMom]

So does the BCM control it?


Sent from my insanely great iPhone 4s using Tapatalk

[LDM]

So does the BCM control it?


Sent from my insanely great iPhone 4s using Tapatalk

"The compressor is an externally controlled variable displacement (ECVD) compressor. The HVAC controls the compressor displacement with a pulse width modulated (PWM) signal. When the A/C switch is pressed, the HVAC requests permission to engage the compressor from the ECM. The ECM must grant this permission before the HVAC can engage the compressor. The BCM acts as a gateway to pass these messages on GMLAN between the HVAC (LS bus) and ECM (HS bus). If the conditions listed above are not met, the engine will not grant this permission and A/C will remain at approximately 4 cc (OFF). The A/C indication (LED/Icon) will remain ON. If A/C pressure is below 196 kPa the A/C will be reduced back to approximately 4 cc (turned OFF) and the A/C indication (LED/Icon) will turn OFF. This is a normal condition in very cold ambient temperatures. While the compressor is running the HVAC transmits a Normalized Load value (representing compressor torque) to the ECM. The ECM uses this value to manage engine torque requirements and maintain idle stability. The A/C will be reduced back to approximately 4 cc (turned OFF) if the HVAC fan is turned to zero (OFF)."

[LDM]

Some more:

The A/C system can be engaged by pressing the A/C switch. The A/C switch will illuminate when the A/C switch is pressed to the ON position. Pressing the A/C switch, the IRC (Radio) sends switch information via GMLAN to the HVAC. The HVAC unit then requests permission to engage the compressor from the ECM. Upon receiving permission from the ECM, the HVAC then engages the compressor.


A/C Pressure is between 196 kPa (28 psi) and 3250 kPa (470 psi).
Engine coolant temperature (ECT) is less than 119°C (250°F).
Engine RPM is more than 400 RPM.
The A/C request signal is set to engage.


Once engaged, the compressor will be disengaged for the following conditions:


A/C Pressure is more than 3250kPa (470 psi).
A/C Pressure is less than 196 kPa (28 psi).
ECT is more than 119°C (246°F).
Throttle position is over 95 percent.
Transmission shift
ECM detects higher than predicted torque load.
ECM detects insufficient idle quality.
ECM detects a hard launch condition.