:)Hi
The AC in my 2004 Malibu was working fine till this morning. When I again took it for a spin I find that the AC is not working properly. At times the compressor will not switch on, sometimes it switches on but after about 20 - 40 seconds it again switches off. I have checked the AC fluid/gas. the pressure reads around 70psi. I understand that there is a switch somewhere that sometimes causes the AC to malfunction. Can someone help?

I'm not sure if 70 PSI is low or high, but there's a sensor in the system that prevents the clutch from energizing if it is too low. You could be right on the border, it could be malfunctioning, or there may be another issue.

You might want to consider going to the auto parts store. There are quite a number of different products, some with gauges, some with leak detector. It's cheaper than a trip to the repair shop and might get you back into freezing up the windows again!

There is a refrigerant pressure sensor on the low side (just follow the low side line back from the compressor). I think the lower threshold is ~30 PSI. If the A/C button stays lit when the compressor cuts out, it probably is a faulty sensor. See a success story in the thread http://www.chevymalibuforum.com/forums/showthread.php?t=2350.

Wrong section, moving this since it is not a 2008+....

Hi, would you be able to tell me where the low side service port for the AC is located in the 2004 Malibu? There is one valve/port right opposite the air intake filter and a bigger valve/port opposite the alternator pulley. is any one of these the low side service port? I understand that the low side service port usually has a blue cap while the high side has a red cap. The caps on both the valves/ports I mentioned are black in color. Would appreciate your help.

Thanks.

Okay, maybe that didn't come out right. The wiring that goes towards the compressor becomes a Y and branches off to the sensor (3-wire connector). The part should look like what's shown on this page (P/N may not be for your Malibu) http://shop.advanceautoparts.com/webapp/wcs/stores/servlet/product_Air-Conditioning-Refrigerant-Pressure-Sensor-ACDelco_15730118-P_432_R|GRP60000_996908362___. The round end is the wiring connector end.

Thanks guys, the excessively high pressure of 70psi on the low side service port got me thinking. My son had charged (topped up) the AC refrigerant and, in so doing, addedd too much gas. This was causing the pressure sensor to malfunction. Let out some of the gas, brought the pressure down to 45psi and, voila, the AC's working as good as new.

Thanks once again to everyone.

Cool! (Yeah that pun was intended!)

Congratulations are in order but the car's A/C system is a closed system that should not need topping up. If there's refrigerant loss, the leak should be found and fixed (involves dyes, evacuation, and recharge). I hope your son has the proper equipment and training to deal with this kind of problem.