Here is my problem: A/C not blowing cold air, blower motor working fine, checked all relevant fuses for A/C and R202 relay under the hood. Everything is fine here. Next, low pressure switch, jumped, clutch does not engage. Next removed relay R202 (clutch relay) measured voltages (at female sockets) where pins 1 and 3 would go, voltage OK. Jumped where pins 3 and 5 would go (bypass to see if clutch engages) and it does. Appears that the pressure switches check out OK (low pressure and A/C cycling switch - although this one not sure). CarMD unit was used as well, and no codes generated so perhaps PCM is working OK? I'm stumped, as a loss of GND by PCM or perhaps a corroded or open wire issue?? Also, possible the A/C switch on the HVAC control could be bad, but the light comes on, (doesn't mean switch is good necessarily). The rest of that unit works fine, control ***** that is, fan speed adjusts properly, air flow looks good. HELP PLEASE! It appears this is an electrical problem where the clutch is not getting juice but I don't know the source of the problem. However, I also noticed that when the clutch/compressor was running (temporarily as described above) cold air still didn't come out. This, I assume, would mean I would need to add refrigerant or re-charge the A/C AFTER I get the clutch to engage electrically. Thanks anyone who can offer some further assistance!

 

Have you verified that the PCM is getting the correct input from the pressure switches so that it can enable clutch operation? Series circuit of fuse F14-High pressure switch - low pressure switch-PCM input? All I see is that you jumpered the low pressure switch.

 

My friend, who knows a lot about cars, checked the pressure switch by jumping it but it did not engage the clutch. He said that switch, therefore, is OK and pressure is OK. Fuse 14 is OK too. The other A/C cycling switch, however, may be a problem but not sure how to test that correctly. My friend and I did not know about that switch until I researched myself yesterday. Apparently, this is a high fault component. But, the CarMD did not indicate any issues in its comprehensive component test (as well as all other tests it does). So, I'm still stumped. Is it possible the clutch is still faulty, even though it engages properly when bypassing the relay? Other than that, my guess is an open or corroded wire in the path to pin 2 of relay (because PCM not activating relay).

 

Okay, you need to go back and READ what I wrote, then follow those hints. Rambling on about other stuff that wasn't asked about won't help diagnose the fault.

You have to actually CHECK the input to the PCM, you cannot just assume it is correct because some sub-components didn't check as faulty.

Unless "CarMD" can read specific PIDs, it's useless for this whole problem as there will not be any DTCs set.