MKI CA20E AC Compressor Clutch Diagnosis

[dustins12]

Hey guys,

So, I just recently cleaned out my blower motor because it was filled with junk and I am trying to get my AC working again.

So, with the car running and the AC on, and the blower at full blast, the clutch doesn't engage at all. I need help trying to diagnose why the clutch doesn't engage. I was looking for a low pressure switch, but can't seem to find one on the car anywhere unless I'm blind. Anyone know where it is? If it doesn't have one, can someone point me in the right direction to start diagnosis on this? I can turn the compressor by hand easily, so its not locked up.

Also, keep in mind, my car now has 102k miles on it, because it just sat for a long period of it's life due to a blown transmission. So I have a feeling that the compressor is good, but something else is causing it to not engage.

Thanks in advance!

[weitrhino]

This may not help you but I just repaired the a/c in one of my Mazdas. It seems that system uses a sensor circuit wired into the blower control to tell the compressor clutch to engage but as the car aged the resistance across connections increased just enough for the voltage at the sensor circuit to fall just out of tolerance. When the fan speed was turned higher the a/c clutch would disengage and that's no good during a Texas summer. The solution was to alter the sensor circuit giving it a wider voltage range for operation by splicing in a voltage divider circuit.  Took a bit of hacking but it works perfectly.

I haven't studied the Nissan system at all but I'd look into exactly how the clutch is signaled.

[dustins12]

Well, I found the low pressure switch. Its attached to the reciever dryer, underneath the front grille. I also went ahead and just hit the valve on the low pressure line to see if anything came out, and nothing did. So its safe to assume that the low pressure switch is doing exactly what its supposed to. So I'm gonna get an A/C Vacuum pump and those gauge things, vacuum the system and then get my hands on some R12 and put some in along with some oil and and see if the system holds pressure.

Also discovered that the compressor for these cars have a "purge" valve on the compressor behind the clutch. It purges when it detects there is too much pressure in the system or if the pressure ever spikes. Not sure if all A/C Systems do this, but its a fun facts.
More updates on this thread to come.

[weitrhino]

It's been a full year, any update on what happened when you recharged the system? Did you find R12 or did you convert to R134?

I'm in the process of converting my A/C and curious to compare notes.

[dustins12]

Haven't been on the forums in awhile. But I ended up converting to R134, and it ran great for quite some time, but then one of the old seals popped and all the refrigerant came out. So, if anyone else plans on doing this, I recommend getting a universal seal kit, and replacing all of the old ones. If I had did that, I would still have A/C lol also, get some wrenches designed for A/C lines. It'll help a lot.

[weitrhino]

I converted to R134 last year, dismantled the entire system, and replaced every seal. You can read up on my process here: https://club-s12.org/forum/index.php/topic,38453.0.html

I tested the system just the other day now that winter in Texas is officially over and it still works perfectly. One worries about the refrigerant leaking over the winter but I've had no issue with that. It was a bitch tearing out the whole system, and a lot of labor, but I'm pretty pleased with the lasting results.