2000 Pontiac Sunfire Problem started after A/C clutch rep

MIKOSH6

MEMBER
2000 PONTIAC SUNFIRE
4 CYL
FWD
AUTOMATIC
120,000 MILES

The A/C clutch on this car needed replacing since it was making a lot of bearing noise when disengaged. It always engaged reliably though when the A/C switch on the dash was pressed. I took the car into the shop and they put on a re-manufactured clutch assembly. Immediately after this repair, when I pressed the A/C switch on the dash, the clutch sometimes wouldn't engage. I returned it to the shop and the mechanic tried making adjustments to the clutch assembly before deciding it was defective and putting on another at no cost.( He mentioned about trying adjustments to the air gap in it ). However, with the second clutch the exact same thing is happening. I decided to do some checking myself. Measuring voltages with a DMM at the clutch relay I found when the clutch didn't engage the voltage on the PCM control side of the clutch relay coil was 14V and when it did engage the voltage measured 0V, so it appears the PCM is sometimes deciding not to allow the A/C to operate. Can you help me out here? Is it possible for a mis-adjusted air gap in the clutch assembly to cause the PCM to shutdown the air conditioning on this car? The only feedback from the A/C to the PCM that I can see is via the Refrigerant Pressure Sensor. I also looked for DTC's and none were present.

2 Replies

2CARPRO JACK

MECHANIC
11,533 POSTS

Have you verified that the switch works every time? Goes to IPC then PCM. If switch has a bad spot, no a/c request is getting out to the controllers

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Wednesday, December 26th, 2007 AT 7:59 AM

MIKOSH6

MEMBER
12 POSTS

Thanks for the prompt reply Jack. :D
No, I didn't do that yet because everything was working fine before the initial clutch replacement. I assumed the problem was probably directly related to the repair. I agree that's not always a safe assumption! I'll pull the switch out and probe with DMM to see if it is sending a signal to IPC.
Do you happen to know on this car, if the PCM calls for A/C on and there is no corresponding change in pressure fed back through the Refrigerant Pressure Sensor, whether the PCM shuts the A/C down? If this was the case and it happens fast I probably wouldn't see it on my DMM and maybe this is a bad clutch or the air gap does need adjustment?