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Old 10-13-2008, 12:36 AM   #1
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Default AC clutch not engaging

Ok so ive gone through the FSM troubleshooting guide and still cant get it to work. Ive verified the following:

-continuity of thermoswitch on the compressor
-continuity between switch and ground (through magnetic clutch)
-no continuity on pressure switch
-continuity between pins of the relay
-checked the two fuses that are involved in the process

Then in desperation, i simply hooked up a 12v source directly to the compressor while the engine was running to see if it would engage, but it did not. Whats the deal?
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Old 10-13-2008, 12:44 AM   #2
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If you apply +12V to the clutch wire the clutch should engage. If it does not, the clutch does not work.
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Old 10-13-2008, 01:34 AM   #3
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crap, so would i be able to swap the stator/magnetic clutch with my bad compressor (bent pulley) without removing the lines? is that likely the part thats not working?

edit: crap x2 ... i threw out the bad compressor ugh.

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Old 10-13-2008, 01:59 AM   #4
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Another thought, could it simply be siezed and need to be tapped to free it up? Thats something i could do.
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Old 10-13-2008, 02:03 AM   #5
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Test it with the engine off. Make sure you got good power going to it. Usually, the mechanical friction part of the clutch goes out, not the electric part. Either way, if the clutch doesn't work it will be easier and cheaper to a used compressor that does work. Lots of $#%@%#* on here remove their A/C, so finding one for cheap shouldn't be hard.
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Old 10-13-2008, 02:35 AM   #6
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well the main thing is i had a shop flush and fill the system and i really dont want to release it or contaminate the lines if i dont have to.
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Old 10-13-2008, 02:51 AM   #7
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Dunno then. You could probably change the clutch that's on it, but GL doing that with the comp on the car. Those things are a bitch.
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Old 10-13-2008, 03:02 AM   #8
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well im gonna hook it up to a 12v source tomorrow and give it a few good taps with a hammer to make sure its not just siezed up ... ill just cross my fingers and hope that does the trick.

if not im going to just say fuckit i think because im going to be selling the car in a few months anyway. just sorta hoped I could get it working because that turns a lot of people away around here.
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Old 10-13-2008, 03:16 PM   #9
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Hell ya! so as it turns out, the compressor is fine, the power source i used wasnt enough power to flip it on when i tested. Going straight from battery source it kicked on without any trouble. Now to figure out why its not getting the power at the plug.
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Old 10-13-2008, 04:19 PM   #10
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Lol, I said "make sure you got good power going to it".

On most domestics, they have a low side and high side safety swtich. If pressure drops too low, the low side safety swtich goes open and the compressor goes off. IIRC, 22PSI and the low side switch goes open on a miata. High side switch works the same way. Pressure goes too high and the switch goes open and the compressor goes off.

To "test" sensors, just unplug them and put a paper clip in them to jumper them. That eliminates 2 possible problems. MAKE SURE YOU GOTS POWER! Like put a new fuse in the A/C circuit. Check fuse with a meter to make sure it's good. Don't ASSume it's by visual inspection alone.

Find A/C compressor relay. Without looking at the wiring diagrams, key on sends +12V to one side of the relay. When you turn the A/C on and all the safety circuits check out ok, the tell the ecu to turn on the compressor, and then the ECU sends out a ground to the other side of the coil on the A/C compressor relay, which closes a set of contacts sending +12V to the compressor. Use a meter and make sure you're getting +12V to one of the contacts and to one side of the coil on the relay. See if the ECU is sending out a ground signal to the relay when you turn the A/C on from inside the car.
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Old 10-13-2008, 11:33 PM   #11
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wow i had some wiring problems for sure. a year and a half ago i replaced the entire ECU harness (spliced it in) and the wire to the thermoswitch was disconnected ... then i also didnt plug the leads to the thermoswitch back in after messing under the dash ... planned on removing all that crap then changed my mind and put it back in, just couldn't hang without heat in the winter.

so I think my AC is working right as of now. I do have to jump the pressure switch for now until i take it back to the shop to top off the freon and then i should be back in business ... Woot!
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