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Randall, RVIA Certification
Category: RV
Satisfied Customers: 11026
Experience:  RVDA/RVIA Master Certified Technician with many years experience.
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I have an RV with a Dometic DuoTherm Brisk Air A/C unit that

Customer Question

I have an RV with a Dometic DuoTherm Brisk Air A/C unit that tries to kill the generator when I turn it on. Every now and then it works great, but most of the time the compressor pulls down the generator immediately and wont run. Also the fan seemed to pull more power than usual and now that wont run on any speed either. This unit is wired only to the genset.
Submitted: 1 year ago.
Category: RV
Expert:  Randall replied 1 year ago.

What is the rated output of the genset? Do you have anything else on so far as AC loads like the fridge or water heater? Did you actually take an AC output reading on the genset to see if it is putting out the proper voltage? I like the one by Electracheck called a Voltage Minder. You can plug it into a plug and it monitors the voltage and cycles and gives you any ground faults or polarity issues. Very handy! This sounds like too low a voltage or inadequate power out of the genset. Try it on shore cord and see if it acts the same. That would be a good way to check it by comparison. Hope that proves helpful here. Please get bak to me if you need more as all follow ups are included in our fee. R.J.

Customer: replied 1 year ago.

I checked voltage output with a volt/ohmeter at 123 ACV --no load, and 121 ACV with the A/C running yesterday. Only ran once the whole day, the rest of the times I tried it, it would just pull down. This unit does not have a shore cord--strictly genset. No other loads on except an overhead light.

Expert:  Randall replied 1 year ago.
How many hours are on the genset? It looks like you have plenty of voltage. Does this A/C unit had a "hard start" kit installed? That would help if you don't have one. About $20 or so and not difficult to install. The other thing would be to use a good amp meter to actually easier to see the draw when starting. It could be the compressor windings are starting to break down. And you might take the leads off (carefully) and measure the ohms resistance between the 3 pairs of pins there. Then see if you have ANY reading between each pin and the casing of the compressor. Let me know what they are.
Expert:  Randall replied 1 year ago.

What did your testing on the A/C compressor show? I am enclosing a link to the Dometic A/C service manual and if you check the section on testing the compressor I think it will be very helpful here. Great to have and I would print out a copy so you have it. R.J.

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