pontiac sunfire compressor turns on and off and system is charged. helpp meeee?

[aaron]

when i turn on the ac the compressor turns on for about 10 seconds and then turns off. it keeps doin it over and over. it isnt blowing cool air but the system is charged. i noticed when im driving i can feel it start to cool but when i slow down or stop the compressor stops and starts over and over again. what could be keepin it from cooling right?

 

[wde3477]

Have you put a set of gauges on the system to read the actual pressures? There is a low-pressure switch that will drop out the compressor below around 22-28psi.

You didn't mention the year, but some of the newer vehicles with R134 freon also use a high-pressure cutout switch.

Are your condenser (in front of the radiator) and evaporator (inside the HVAC fan / heater enclosure) coils clear?

Not sure if your model year uses a cycling clutch or an expansion valve setup. It is normal for a cycling clutch system to kick in and drop out if the cooling load isn't too great - however, it sounds like this isn't the case. Also, may have a blockage somewhere in the lines.

If you haven't worked on A/C systems before, my advice would be to take it to a professional. The extreme temperatures and high pressures involved with AC systems can cause further equipment damage and significant personal injury if the work is not done properly.

Good luck, and keep us posted on your findings.

 

[05sunfireman]

About the compressor

I own a 2005 Pontiac sunfire and it was acting up doing the same thing. I took it to my mechanic and he said that the ECU ( engine control unit) went bad and he change it out. It fixed that problem, but they programed it with a check engine light on so when i go to fix that problem the car acts up again. so if they repair it, make sure they program it right. also the new ecu and programming cost me $800. Oh and my car only has 30,000 miles on it, so i don't know why it would have gone bad.