A/C Compressor not engaging


New Member
Oct 13, 2018
Hampton Virginia
I have a 3.8L V6 Mustang. Problem is, when I turn the A/C switch, the blower and radiator fan runs but the compressor clutch does not engage.. it's getting 14.5v from the connector. I've tried "Hot wiring" to the battery with some extra leads and that seemed to work. Freeon is topped off. Could there be an issue with the CCRM? Or am I overlooking something?
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SN Certified Technician
Aug 14, 2009
Houston Texas
it's getting 14.5v from the connector.
^^^this is an important clue. IF there is battery voltage at the AC compressor clutch this "proves" that the CCRM is good and everything is calling for the clutch to engage. The fact that a battery voltage bypass at the clutch does not cause the clutch to engage further points to a clutch electrical problem. IMO you should focus on:
  • The AC clutch itself
  • The ground for the AC clutch.
If this were my car the first test would be to confirm there's a good ground from the AC clutch. Use a test light that will "load" the circuit. Put the test light pig tail on battery positive. Confirm the test light works by probing battery negative. Now probe the ground side of the AC clutch connector. Is the test light bright?

Assuming a good ground, next measure the Ohm resistance of the coil with the electrical connector disconnected. What is this value?
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