Question about Dometic Rooftop RV Air Conditioner

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Roof top AC unit on travel trailer hums as if trying to run even when turned off at thermostat. Eventually pops 30 amp main circuit breaker (not just A/C circuit breaker). I've turned the 20 amp A/C breaker off to stop the problem for now and wonder if anyone has an idea of what might be wrong.

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Hi, this sounds to me as though your compressor is locked up and what happens is it will overheat and before it can trip its own overload, it is drawing enough amperage to trip your 30 amp main breaker! If you are able to get up top and remove the cover on the unit, have a friend turn it on and see if you can see if its the black compressor humming, or the condenser fan motor which should also be up and running. If you can isolate which part it is such as that motor, or if it is the compressor which I am sure it is because it is the one part that would draw enough amperage with a locked rotor, ( L. R.A. ) to trip the 20 amp or 30 amp breaker. Do this check when the unit has set over night and the compressor will be cool to the touch. Now, when its first turned on if the compressor just hums at that time, you will have a locked rotor. We have what we call a hard start kit which is basicly a very strong start capacitor and relay that we install in series with your run capacitor that sometimes will break free a stuck compressor or a tight one. You should also look at your capacitor to see if it is swollen, leaking oil, burned terminals or any deformaty. It will look simular to a chrome soda can or a rectangular shaped chrome part that has wire terminals coming off the top. If it is a dual capacitor, it will have markings on the top such as a C- for common, Herm for hermetic compressor, F for the condenser fan motor on top. Try and locate this and look it over. If it is bad, this will cause both the fan and compressor to just set there and hum and over heat until the breaker trips. These are things you can check your self to narrow it down, but if it is the compressor, you will need a a/c repairman to do the repairs it needs. If you can see if the capacitor is in any of the conditions that I said earlier, make your self a drawing of it and mark how and color of wires attach to it and take it to a appliance repair retail store/ shop and they can check to see if it has the correct values like 5uf x 25 uf x 370 volts which ever it calls for. The cost for one is around $15. If this is the problem, it will be a quick fix for you and save you a bundle. Does the indoor blower put out air? If so thats good, the problem will be the run capacitor, compressor or condenser fan and hopefully not all 3!! Please don't forget to rate me on this and please keep me posted also. You may want to do the same with the thermostat if its not shutting off the unit. Take it in also if you think the run cap is faulty, but remember to write down the wire connections and it should be lettered such as R, G, Y, W. Please keep me posted.
A/C, Heating, & Refrigeration Contractor

Posted on Aug 28, 2010

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Recently purchased a 4400W generator to operate travel trailer primarily and on occasion my ac unit. Connected the generator to the travel trailer, then ran the a/c, everything going well, then the circuit...

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I need a second roof top air conditioner in my fifth wheel But there is no vent in bedroom Is it still possible to have one installed

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High amp draw can be caused by a few different things, so first check that incoming voltage to trailer is sufficient. (115 volts) Not unusual for some parks to install more hydro hook-ups on a feed line, and when all are up and running, your incoming voltage could be decreased. If your o.k. that way, then I'd start looking at the compressor circuit of your ac, in particular, the compressor start-up capacitor. The capacitor basically stores electricity and boosts it to higher voltage for compressor and fan start-ups to reduce current draw that will trip the breaker. Please have a knowledgeable electrician, or RV tech check this for you, as a capacitor can give a real good high voltage (possible fatal) shock, even when power is off to unit. I also suspect that the start relay has shorted (welded) itself due to high amp draw situation, and that is reason it comes on by itself.

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1 Answer

What could cause my RV air conditioner to "pop" the breaker

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Jun 01, 2010 | Dometic Rooftop RV Air Conditioner

1 Answer

Wiring issue on a 1965 Roadrunner Travel Trailer

Generic comments follow:

I'm not real clear on what you are asking ... I can almost guarantee you that you will not find a wiring diagram for your trailer.

Your travel trailer operates on 12 V DC. Your frig, the heater, all the lights, radio, all 12 volts. Your running lights should be getting power from the tow vehicle. While towing, the tow vehicle should be charging the battery. You may find some 110 volt lights inside, but probably not. To keep your battery charged, you have 110 Volt AC power coming in. Your frig may run on 110 V AC but it still needs 12 volts for control. Your Air Cond and Microwave and TV (if equipped) will al,so run on 110.

Regarding the three wires from the battery, there should be a battery charger close by your 12 Volt fuse panel. Even though the trailer is a "vehicle" dont depend on using the frame as a ground like you would in a car. So, that accounts for two of the three - a red or black and a white wire. There may be some dedicated line that the battery supplied to account for the third wire.

There should be a emergency breakaway switch on the front of the trailer. This is a switch with a pull pin. If the trailer breaks away, the pin is pulled out by the tow vehicle and the electric brakes should be automatiocally applied to stop the trailer. This switch should be powered, unfused, directly from the traailer battery and go directly to the electric brakes - presuming you have this feature.

Be aware, this trailer power supply was built and designed for a life style far different from that we enjoy today. If you have a 30 amp cord, as I suspect, 30 amps is enough to charge your battery, run your 12 volt items, run a TV and AC or TV and Micro or Micro and AC but not much else. As you are aware, you have two circuits built with #12 and they are probably protected with a 15 amp breaker though the #12 would be protected with 20 amp breaker in a house. The cord is only rated for 30 amps and it may be tired, unless you have replaced it.

I hope I have provided a little insight to your situation. If I can be of further assistance, please let me know.


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Drain for a colelam rv air conditioer

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1 Answer

Breaker trips on roof top RV A/C

check your breaker is it hot to the touch?
check the wire tightness at the breaker?
remove the circuit breaker and inspect the terminals on the breaker and in the panel and the breaker itself for signs of overheating and discoloration due to the fact
check the connections at the unit itself
check that you have proper voltage to your unit
find the nameplate and look for FLA full load amp draw
is the breaker properly sized for the unit and is the wire size correct for the breaker?
(Check nameplate on unit)
buy a clamp on amp meter and see if it is under or over the nameplate rating when unit is running
take great care when you venture into electric,if you arent comfortable find someone who is.
you may have a weak breaker if all the above pass?
Replace it

Jul 05, 2009 | Dometic Rooftop RV Air Conditioner

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