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Author Topic: MKI CA20E AC Compressor Clutch Diagnosis  (Read 133 times)

Offline dustins12

MKI CA20E AC Compressor Clutch Diagnosis
« on: 03:47:11 PM / 17-Jun-17 »
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!
« Last Edit: 03:49:26 PM / 17-Jun-17 by dustins12 »

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Offline weitrhino

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Re: MKI CA20E AC Compressor Clutch Diagnosis
« Reply #1 on: 09:00:01 AM / 19-Jun-17 »
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.
« Last Edit: 09:01:39 AM / 19-Jun-17 by weitrhino »

Offline dustins12

Re: MKI CA20E AC Compressor Clutch Diagnosis
« Reply #2 on: 09:54:47 AM / 22-Jun-17 »
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.
« Last Edit: 09:55:38 AM / 22-Jun-17 by dustins12 »