Forum Discussion

thebat68's avatar
thebat68
Explorer
Jul 02, 2016

Upgrade to 50amp - now AC doesn't work

Okay, so a few weeks ago went out to the TT to get it ready for a trip and my AC had died. I replaced with a new Dometic Brisk II and it seemed to working great at home.
I had planned a 50amp upgrade from my 30 and did that yesterday. Everything seems to work, except that the AC doesn't kick on. Now, I'm only plugged into my house 20 amp circuit, but the AC always worked before on it with no issues.
Is there some reason with the way that 50amp service works that my AC shouldn't work - is it somehow getting much less amperage?
I have double-checked all the connections in the circuit box and everything is tight - even put a meter on the breaker to make sure it wasn't bad.
I don't have a 50 or 30 amp source readily available to try, which is why I'm normally just plugged into the house wiring.

25 Replies

  • RoyB's avatar
    RoyB
    Explorer II
    I guess you can use two RV adapters 30-50 and then a 30-15 and that should feed both 50AMP zones in your trailer from a 20A Recetacle from the garage area... Doing this of course you only have 20AMPS being divided up by all of your appliances in the trailer in both zones... You will have to turn off ONE Air Conditioner for sure to keep from tripping the 20AMp Breaker in the house...



    RV30-50 Adapter - Note the two 50A side HOTS are tied together here...


    RV30-15 Adapter


    Roy Ken
  • Do you have a fully charged battery to operate the thermostat correctly?

    A meter would tell where there is power and where there is none.

    Don't know exactly about your A/C wiring but some systems have a delay incorporated.
  • You have the a/c on the hot leg your 20 amp is not supplying. That is just my guess. Do you have a dog bone 50-20 or how are you hooked up.
  • Sam Spade wrote:
    Then: Plugging a 50 amp vehicle into a 20 amp outlet may mean that only one side of the 50 amp service is hot and the other side is dead......and that would be normal.


    Of course this isn't "normal" ... if one uses a 15 amp male > 50 amp female dogbone to plug a trailer properly wired with 50 amp main service into 15 amp or 20 amp service both legs of that 50 amp main service into the trailer will be powered, limited of course to a maximum draw of 15 or 20 amps across both legs, in which case the A/C, no matter which leg it's wired to, would receive power ... provided of course that this wiring the OP did was done correctly. ;)
  • The odds are good that you wired something wrong. But see below.
    Is the A/C actually getting 120V power ?
    Is the thermostat getting the low voltage that it needs ?

    Then: Plugging a 50 amp vehicle into a 20 amp outlet may mean that only one side of the 50 amp service is hot and the other side is dead......and that would be normal.

About DIY Maintenance

RV projects you can tackle on your own with a few friendly pointers.4,382 PostsLatest Activity: Jul 26, 2025