Dometic A/C unit instantly Tripping Breaker

[EricS88]

Hello all new member looking for some help. I have a 2009 Keystone Sprinter SS with a dometic 13,500 btu ac unit that i am having issues with. Last year it quit working on me when i took it out last and didn't get around to fixing it till this season. It was at the time blowing the 3 amp fuse up in the control module which completely disabled the use of my furnace or my ac. So i went and ordered a new control module for the unit and installed it this morning. Now I have a working furnace however when I flip the breaker to supply power for the a/c it instantly trips the breaker in the camper. almost as if I had a hot wire crossed on a ground. I don't even have the thermostat set to a/c when I turn the power on. This module I put in is not exactly the same as my original one as they no longer make it. I did however download a installation manual for it and made sure everything is installed as it should be from what I can tell. This unit is supposed to be a direct replacement. Is there anything else I should be looking at or that I'm missing that would cause the breaker to trip instantly? I'm wondering if I have a wiring problem up on the roof or a bad component of some sort? I have done some research before posting and everything I have seen is talking about the breaker tripping after 5 minutes of use or more. Mine is instant. Any help or guidance is greatly appreciated.

[cavie]

Originally Posted by EricS88

Hello all new member looking for some help. I have a 2009 Keystone Sprinter SS with a dometic 13,500 btu ac unit that i am having issues with. Last year it quit working on me when i took it out last and didn't get around to fixing it till this season. It was at the time blowing the 3 amp fuse up in the control module which completely disabled the use of my furnace or my ac. So i went and ordered a new control module for the unit and installed it this morning. Now I have a working furnace however when I flip the breaker to supply power for the a/c it instantly trips the breaker in the camper. almost as if I had a hot wire crossed on a ground. I don't even have the thermostat set to a/c when I turn the power on. This module I put in is not exactly the same as my original one as they no longer make it. I did however download a installation manual for it and made sure everything is installed as it should be from what I can tell. This unit is supposed to be a direct replacement. Is there anything else I should be looking at or that I'm missing that would cause the breaker to trip instantly? I'm wondering if I have a wiring problem up on the roof or a bad component of some sort? I have done some research before posting and everything I have seen is talking about the breaker tripping after 5 minutes of use or more. Mine is instant. Any help or guidance is greatly appreciated.

Get a helper. you need to be on the roof and at the t-stat at the same time.

Go up on the roof, remove the cover and remove the wires from the trailer to the AC contactor. The wires feeding the unit. While your there, spin the fan motor. Turn on the AC at the thermostat. If there is no trip the problem is in the unit. If the fan motor spun freely when you tried it then the problem is in the compressor.

Now hook up the supply wires to the contractor. Remove the wires to the compressor on the other side. Turn on the fan at the t-stat. See it runs. Turn it off. Now remove the fan wires from the load side and hook up the compressor wires. Turn it on. See what happens. This is how to troubleshoot. You must check each item individually.

[EricS88]

Thanks for the response. Since I just posted. I went back out to try some more. What I did was unplug the ac unit from the new module I put in and flipped the breaker to see if it was the ac unit tripping it or something else. When I flipped that breaker I instantly found the problem. Wow I had smoke coming from the unit. Turns out the new unit I put in on the clamp that holds the 120v supply wires in place had a sharp burr on the inside. When I had clamped it down to hold the wires in that burr cut through the hot wire which caused it to short and burnt the hot wire right though. That was super scary and I got lucky no fire started from it. I pulled it apart and filed the burr out recut the wires and now everything works great. I'm tempted to email the company about this part as I feel they need to watch closely at this stuff. This could have burnt my trailer down. Then again I should have watched closer myself too. I know I will from now on

[Bama Rambler]

So the clamp on the new control box (or board) had a sharp burr that pierced the hot wire insulation? Yeah, I'd definitely let the mfg. know.

Was it a Dometic part of an aftermarket unit?

Thanks for coming back and letting us know what you found.

[EricS88]

Yes that's correct on the new control box. It was a dometic control box

[Witch Doctor]

If you where tripping the breaker, more then likely you have a grounded compressor, how you check is to remove the wires from the compressor terminals, should be 3, then take a ohem meter and and touch the compressor skin or the copper suction line with 1 terminal then with the other touch all 3 one at a time. You should have start, common and run. If your meter needle moves at all your have a grounded compressor, new unit time. Hope that helps. That means a winding is touching ground and it will blow the breaker every time you switch it on. There is no repair for that without a new compressor.

[boondocking]

^^
Or a sharp blur on the wire hold down clamp that pierced the wire and grounded it out.