Compressor won't engage

SWALTERS2007

MEMBER
2000 SATURN
4 CYL
FWD
AUTOMATIC
155,000 MILES

Interior fan works, a/c light comes on when I push the button. Gage is over 100# (static). Pressure switch is good (it's on the high side of compressor, no switch on suction side?). Fuse and relay in fuse box under hood are good. If I had a diagram I might know where to look next. I haven't powered the a/c clutch directly yet. What is my next step? Is there some type of control module that is interrupting the signal?

1 Reply

MERLIN2021

MECHANIC
17,250 POSTS

1. Ensure IGN3 fuse (10-amp) and HVAC SW fuse (20-amp), both located in instrument panel fuse block, are okay. Ensure IGN3A fuse (10-amp) and A/C fuse (10-amp), both located in underhood fuse panel, are okay. If fuse(s) are okay, go to step

2. Check for a short to ground in Dark Green wire between underhood fuse block terminal E4 and A/C compressor. Repair as necessary. Remove A/C diode from underhood fuse block and ensure proper operation. Ensure resistance of compressor clutch coil is 3-4 ohms while hot and cold. Ensure proper compressor operation.

3. Turn ignition off. Replace A/C control relay, in underhood fuse block, with a known-good relay (keep old relay). Turn ignition on. Check A/C compressor operation. If A/C compressor operates, discard old relay. If A/C compressor does not operate, turn ignition off, reinstall original relay and go to next step.

4. Turn ignition on. Check for voltage between ground and A/C compressor clutch connector Dark Green wire terminal "B". If battery voltage is not present, turn ignition off and go to next step. If battery voltage is present, replace A/C compressor clutch. Ensure proper compressor operation.

5. Locate Body Control Module (BCM) and disconnect 16-pin connector. Turn ignition on. Using DVOM, check for voltage at terminal B8 (Green/White wire). If voltage is not present, go to next step. If voltage is present, go to step 7.

6. Check for voltage at A/C-heater control panel (HVAC control head) terminal B5 (Green/White wire). If voltage is not present, replace A/C-heater control panel. If voltage is present, check for open in Green/White wire and repair as necessary.

7. Turn ignition off. Disconnect PCM. On 2.2L engine equipped models, connect jumper wire between connector J2 terminal No. 55 (Gray wire) and ground. On 3.0L engine equipped models, connect jumper wire between connector J2 terminal No. 13 (Black/White wire) and ground. Turn ignition on (either engine). If A/C compressor operates, replace PCM. If A/C compressor does not operate, go to next step.

8. Turn ignition on. On 2.2L engine equipped models, check for voltage at connector C1 terminal C4 (Gray wire). On 3.0L engine equipped models, check for voltage at connector C2 terminal B6 (Black wire). If voltage is not present, check A/C relay operation. If voltage is present, check for open in appropriate wire.