Question about Dometic Rooftop RV Air Conditioner

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Heat stripe and compressor on at the same time

I have a similiar problem with my Duo Therm. When I select the cool position on the t-stat both the heat strip and the compressor try to kick on. This is overloading the 20amp circuit. I am still struggling to find out why this is happening. I have replace both the t-stat and the relay board and still haven,t found the problem.

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  • mark_roge357 Jul 09, 2009

    Jeff, thanks for your help. With further investigation the problem was this: I needed a new t-stat so I went to the supply store and showed them my old one and he gave me a new one. The problem is one is for a heat strip and the other is for a heat pump. If you look carefully at the circuit board you will notice a difference at to where the diodes are placed. I unsoldered the diodes in the new t-stat and positioned them like the old t-stat and the unit is working fine. Thanks again

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Is this a wall mount thermostat or manual control unit? What is the model of the air conditioner? The only way that this is going to happen is that power is jumping somewhere to the heater coil from the cool side.

If it is a wall mount thermostat, the yellow wire is the cool mode (compressor on) and both the tan and blue wires are the fan mode. The orange wire is for the heat strip. So if you set the thermostat on High/Cool, then you should have power at the yellow and blue wires, not the orange. If the orange wire is energized, then there is a problem.

Remove the orange wire from the thermostat, try it again. If the breaker trips, then remove the wire from the connection at the relay board. Once again, try the unit. If the breaker trips due to the same problem, then it has to be a bad relay board. If the breaker does not trip this time, then you have problem with your wiring between your thermostat and the control unit.

Sounds like you don't have manual controls since it has a relay board.

Hope this helps,

Jeff


Posted on Jul 03, 2009

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