AC Clutch Will Not Engage? -

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Old 02-21-2010, 10:00 AM   #1
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Default AC Clutch Will Not Engage?

AC stoped blowign cold. I thought my freon was low and went to charge. However the ac clutch will not engage to allow a recharge. (the clutch engaging is probably my problem, and not the freon.)

I located the low pressure switch and installed a jump wire and the ac clutch did not engage. I am getting power to the low pressure switch and the jump wire. I would not be getting power to the low pressure switch if the relay in the ccrm was bad, right? Any ideas on why the clutch will not engage?

There is no voltage at the compressor or the low pressure switch connection at the compressor (even when jumped). The clutch will spin freely with some resistance so there has to be some freon in the system. The clutch is properly gapped at about .35. Any ideas?
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Old 02-21-2010, 04:48 PM   #2
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It's possible that the pressure in the a/c system may be too low from a leak. If so, the compressor's clutch will not engage until the pressure increases above a specified design psi in order to prevent internal damage to the compressor(a/c gas contains oil that lubricates the compressor).

Also, your car's A/C system has 2 pressure switches:
- One disables the compressor's clutch mechanism if the pressure gets too low.
- The other cycles the compressor's clutch on and off during normal operation.
Did you check both switches?

Other possible causes are 2 relays.

Last edited by ski; 02-21-2010 at 04:51 PM.
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Old 02-21-2010, 07:00 PM   #3
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It's obviously an electrical issue. If you jumped the switch but no power is getting to the compressor, then no power is getting to the switch either. Did you check that power was getting up to the jump you made? If not then you have to track further back on the system. Relays, fuses, SJB, all these and the switch on the dash may all be problems you have to track down one at a time. The clutch will kick on for most AC units anywhere above 25psi, if Freon was the issue. Was the AC cycling on and off often or quickly before this happened? That would generally be an indicator of low Freon which could have caused a burn out somewhere.
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Old 11-30-2013, 04:21 PM   #4
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Default A/C clutch not engaging

Hi to all,

I have a 2002 Mustang GT and the A/C clutch is not engaging. I attached a wire straight from the battery to the Compressor and it started blowing cold air, also the a/c clutch engaged. Can anybody tell me what else can I do to find out what is wrong? Also, I tried to bypass the pressure switch next to the dryer with a paper clip but it didn't worked.
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