!!!DANGER!!! !!!WARNING!!! Exploding A/C clutches!!!!

Heating / Cooling / AC

  1. 67Dart273

    67Dart273 FABO Gold Member FABO Gold Member

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    Heh.........I admit the headline was to get your attention. This morning, started to finish the engine conversion in the White Whale III to add an A/C compressor

    Went through the "pile," and I've lost count. Two were earlier TBI era compressors.....completely different mount and hookup. One both clutch and compressor are completely frozen. One turns but "grates." The last two THE CLUTCHES TESTED SHORTED..........which brings me to........

    How NOT to blow up your A/C compressor clutch!!!!

    It turns out that (at least on the later Dodge RAM/ Dakota/Durango) that there is a spike protection diode IN THE PIGTAIL of the compressor. If you TRY TO BENCH TEST this by hooking 12V to the clutch, AND IF you get the battery polarity incorrect, YOU WILL SHORT that diode, and "easy to assume" the clutch is "bad."

    (A normal clutch reads upwards of 3+---4 ohms. A shorted diode reads a fraction of an ohm.........)

    But I'm suspicious. So I cut the pigtail in half, pulled the protection sleeve off, and........................

    IMG_0978.JPG

    IMG_0979.JPG

    (Cutting the pigtail............I would not have done this except this will be "underdash" hang on NON OEM air. So the original harness connector will not be used)
     
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    • Revhendo

      Revhendo Master ACME Tech

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      I never knew that. Thanks for the heads up.
       
    • dibbons

      dibbons Well-Known Member

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      I retrofitted a 1990's era Mazda MPV (had been an Alaskan rental car) with a complete A/C system from a junkyard. Before getting it charged, I bypassed the low-pressure safety valve to see if the compressor would kick it. It kicked in alright, for a few seconds, then locked up. Spent a couple hundred dollars more for another compressor, then everything worked as it should. Assumed I destroyed the compressor, probably did.
       
      Last edited: Jul 2, 2017
    • 67Dart273

      67Dart273 FABO Gold Member FABO Gold Member

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      ^^That's a somewhat different problem. Likely no oil in the compressor^^
       
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      • SIX225

        SIX225 Well-Known Member

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        Diodes are often put on coils to protect the driver on the circuit that controls it. I'D put one back in.
         
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        • 67Dart273

          67Dart273 FABO Gold Member FABO Gold Member

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          As I mentioned in my post.............yes, I know exactly why it's there........LOL

          Anyone want to doubt the validity, "hold onto the test leads when you disconnect the clutch from the battery............
           
          Last edited: Jul 2, 2017
        • nm9stheham

          nm9stheham Well-Known Member

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          Yep, I was reeeal careful with polarity when testing and installing for this very reason when I replaced the clutch on my '07 Ram.
           
        • 67Dart273

          67Dart273 FABO Gold Member FABO Gold Member

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          The good news is I got all the bracket/ compressor installed and the truck running again. Now I'm waiting for the eBay/ Chineseaotionized "throw under the dash" evap unit

          Ebayevap.jpg

          Then the fun will begin..........gathering up enough junk to hook it all together. I don't think I have a good condenser out of the "Whale series" pickups (junker was WWII) so I'll use the condenser out of the A body I junked. I'll have to rework those hoses
           
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