2012 GT AC Clutch Locks Up Without AC On!?!

Discussion in '2011+ Mustang GT 5.0L Tech' started by craigarbo, Aug 18, 2018.

  1. craigarbo

    craigarbo Junior Member

    So, the AC in my 2012 Mustang went out...at 60K. The clutch was burned up. I just changed out the clutch and when the AC is on, the AC blows cold. Just like it should. But, if/when I turn off the AC, the compressor/clutch locks up. Of course the belt still runs over the pulley but the pulley doesn't freewheel. So, I guess I will be running the AC full time until I get this figured out. I'm going to assume this is exactly the same reason the clutch went out last time. Anyone here have any clue as to WTF is happening here? Thanks in advance.
  2. Wes06

    Wes06 forum member

    hmm, how would the pulley actually stop turning if the clutch was locked up? it should just keep the compressor turning.

    unless the compressor is locked up I dont see how it could really lock up the pulley, which would then burn through the belt in no time.

    100% sure that the pulley doesnt free wheel, and just the face of it is staying still?
  3. travelers

    travelers Senior Member

    Put a volt meter on the feed wire and see if there is still voltage holding the clutch engage after you turn it off.
  4. roegs

    roegs Junior Member

    Is your mode selector set in Defrost position? Defrost can run the compressor even if the regular AC is off.
  5. msvela448

    msvela448 forum member

    When it went out the first time did you replace it yourself or have a shop do it? The reason I ask is that there are little washers under the single bolt on the front that holds the clutch assembly to the compressor shaft. They make different thickness washers to create the desired gap between the clutch surface and the pulley face... I think it should be about .014" (but that's from memory).

    To see if your pulley free wheels just take the belt off and spin it by hand. It should be very smooth and spin very easily like an idler pulley... If it doesn't then that's your problem... The clutch face isn't spaced out far enough from the pulley face. My guess would be the washers are missing, or the wrong ones are installed, or they are installed on the wrong side under the bolt head instead of in the clutch face side to move it out and away from the pulley.

    If everything checks out then you might have a problem with the coil wires being shorted. Put everything back together but unplug the coil (small two wire plug on the a/c compressor) . Start the car and see if it free wheels (the clutch face should stay still while the pulley spins). If it does then start checking the wires for being pinched or melted.

    Hope this helps.

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