PDA

View Full Version : 2001 Air conditioning problems, Possible bad PCM?


lowandrusty
07-11-2017, 01:57 PM
Helping a coworker with their Miata. I've been through the diagnostic tests multiple times with this car.
car had no A/C, did a bit of troubleshooting and found It had corroded/broken wires at both the compressor and condenser fan relays. I replaced the broken wires, connectors and relays. Recovered the refrigerant, evacuated the system and refilled it just to make sure we had a proper charge. Cranked the car up and hit the A/C button with no compressor engagement. I was puzzled so I started doing voltage and continuity tests. At this point Everything has passed, but the PCM just isn't grounding the relays. I was suspecting the thermostatic switch, but I have power at the A/C fan relay. When bypassing the PCM and grounding the relays, I have A/C. Is it common for the PCM to fail on these cars? I never had a problem with any of the PCMs on the NAs I've owned.
Anything I'm overlooking or should retest?
kung fu jesus
07-11-2017, 02:16 PM
I think you could be correct, but adding the AC to a car that didn't previously have it, I am suspect maybe there is a missed connection in the cabin? I have only worked on a '99 and '92 for AC work.

Do you have this diagram?

http://www.mellens.net/mazda/mazda_miata_extra_manual/2001_wiring.pdf
Martin
07-11-2017, 02:32 PM
I had to replace the PCM in my car a couple weeks ago (and a relay) to get the a/c working. The PCM wasn't grounding properly. At least that's what the shop told me.

My car isn't a 2001 - I'm just saying that the PCM could be the problem.
lowandrusty
07-11-2017, 02:33 PM
I think you could be correct, but adding the AC to a car that didn't previously have it, I am suspect maybe there is a missed connection in the cabin? I have only worked on a '99 and '92 for AC work.

Do you have this diagram?

http://www.mellens.net/mazda/mazda_miata_extra_manual/2001_wiring.pdf


HAHA
No, the car was equipped with A/C! When I said "car had no A/C" I meant inoperative A/C! lol
kung fu jesus
07-11-2017, 03:08 PM
OOOOooooooh! Moving along... :)
lowandrusty
07-11-2017, 03:10 PM
OOOOooooooh! Moving along... :)

Also, yes, I do have the wiring diagrams. I do appreciate the link though!
RotorNutFD3S
07-11-2017, 04:00 PM
It's not common for the PCM to fail and cause this issue, but I've heard of it happening. I'm trying to remember how the NB2 immobilizer works with the PCM (and am failing to recall), but I'd suggest locating a known good PCM and swapping to test.
lowandrusty
07-12-2017, 07:58 AM
It's not common for the PCM to fail and cause this issue, but I've heard of it happening. I'm trying to remember how the NB2 immobilizer works with the PCM (and am failing to recall), but I'd suggest locating a known good PCM and swapping to test.

Yeah, it's really looking like the pcm is the culprit here. Time to start shopping around I guess.