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nebrady's avatar
nebrady
Visitor
Jun 28, 2026

New Fridge, Old Coach

I recently installed a Norcold Polar 7 fridge in my Mother's older (1991 era) motorhome.   She never uses it, but likes to keep it around and keeps it maintained.    The Norcold works wonderfully on propane, however when the coach is plugged in, it will not run on AC.   If I disconnect the fridge from the outlet (on the outside vent) and plug the fridge directly into shore power via an extension cord, it works fine.   

I am not an electrician by any means, but I am guessing that since the coach shore power is running through the original power converter, that the new Norcold does not like the "dirty power".   The outlet has 120v and I can plug in other things like a fan into the outlet and it works fine.  As I mentioned, I can plug the fridge directly into shore power (bypassing the power converter) and it works exactly right.   

If I am correct on the "dirty power" concept, what is the method of resolving the issue, besides installing a modern power converter?

6 Replies

  • Grit_dog's avatar
    Grit_dog
    Trailblazer
    Jun 29, 2026

    Are you confusing converter with inverter?

    You didn’t say that it didn’t work with the camper plugged into shore power.  Just that it worked if plugged in directly from shore power to fridge.  Does the camper have other AC components? Do they work?

    If you’re getting AC from an inverter, it may not have the amperage to run the fridge compressor on AC. 

    • nebrady's avatar
      nebrady
      Visitor
      Jun 28, 2026

      Yes.  It has 120v at the outlet.   I not only tested it with a Fluke mulitmeter, but plugged in a fan which ran fine. 

       

      • StirCrazy's avatar
        StirCrazy
        Moderator
        Jun 29, 2026

        hmm its not because of dirty power, as nothing changes the shore power, the converter only changes 120V AC from shore to 12V dc, your 120V AC plugs are just fed directly from shore through the breaker panel.

        the only thing I can thing of is maybe somthing is wired wrong between the shore power to the outlet.  I would pull the cover off the outlet and see how that looks, then work my way back.  

  • nebrady's avatar
    nebrady
    Visitor
    Jun 28, 2026

    Brand new battery.   I  purchased and replaced it last Monday.    That was one of my thoughts too, but it did not change anything.   Still will not run off of the coach outlet, but runs great off of an extension cord bypassing the outlet.    Outlet shows 120volts.  

  • way2roll's avatar
    way2roll
    Trailblazer
    Jun 28, 2026

    What's the state of charge of your house batteries? The fridge is probably running from the house batteries and the shore power charges the batteries.

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