Forum Discussion

nebrady's avatar
nebrady
Explorer II
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?

17 Replies

  • Grit_dog's avatar
    Grit_dog
    Trailblazer
    Jul 02, 2026

    This is perplexing.  
    First, if anything didn’t work it should be the load (fridge heater) pulling too much power which would trip the breaker. The fact that it won’t run off any of the outlets but AC and micro work is even more confusing. Is the micro a plug in, have you tried that outlet?  Micro should draw more power than the absorption fridge on AC. 
    Im sufficiently perplexed. 

  • 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
      Explorer II
      Jun 29, 2026

      Everything else works.  AC, microwave, outlets etc...   No issues.   The only thing that will not work is the refrigerator when plugged into the coach outlet.   I even plugged the refrigerator into an extension cord and plugged the cord into another outlet on the coach and it would not run the fridge.   

      It will run on gas with no issue.   As soon as I plug in the coach to shore power, it will attempt to switch over to AC and then immediatly shut down.  

      I am completly out of ideas.   

      • stevenal's avatar
        stevenal
        Nomad II
        Jul 01, 2026

        AC comes in through the main breaker, then distributes out. One circuit will be to the converter keeping the battery charged and running DC loads. Another will go to the fridge AC receptacle. It is possible the converter is throwing harmonics back on the system, making the power "dirty." Easy to test, simply open the breaker to the converter. 

        I would open and close all the breakers, and try again. Also check the voltage at the receptacle when the fan is plugged in and running. If the voltage drops, you have a bad connection somewhere, or a bad breaker. Since the other coach receptacles are affected, I would look first at the main breaker.

        Also, what are you using for shore power, and have you tried other sources?

    • nebrady's avatar
      nebrady
      Explorer II
      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
        Jul 02, 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. 

        how far apart are the breaker and the outlet for the fridge 120V?  I know my next step would be to use your multimeter on Ohm setting and see what the resistance on each leg is.  that would rule out wiring issues that maybe would run a fan but not somthing that draws more power. 

        one thing is kinda confusing, maybe you could clear this up.  when your trying to run it on 120V are you plugged into shore power or running from your batteries on an inverter?  

         

  • nebrady's avatar
    nebrady
    Explorer II
    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.

      • StirCrazy's avatar
        StirCrazy
        Moderator
        Jul 02, 2026

        the workings of the fridge are still controled by 12V, only the heating element is run off the 120V

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