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Randall, RVIA Certification
Category: RV
Satisfied Customers: 11889
Experience:  RVDA/RVIA Master Certified Technician with many years experience.
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Ho gene, we have a new dynamax rv with two dometec air

Customer Question

Ho gene, hi we have a new dynamax rv with two dometec air units.... they both work but won't run at the same time on genset or 50 amp power
JA: Have you checked all the fuses? Do you have a wiring diagram?
Customer: Yes, fuses all good, breakers all good....both units work, but they cycle one on one off
JA: What is the model of your '50 RV?
Customer: Dynamax dx3
JA: Are you fixing your RV yourself? What have you tried so far?
Customer: We are trying tomtroubleshoot while,on the road, it is hot and we have to keep truck running so dash air will help single air keep up
JA: Anything else you want the mechanic to know before I connect you?
Customer: The rv is new 2017, and this is our first trip.... everyone tries to tell us we are only on 30 amp power or that genset is not big enough..... we have an identical dynamax dx3 with us on thsi trip and it runs both airs at the same time, but dow but does not have a fancy digital thermostat
Submitted: 2 months ago.
Category: RV
Expert:  Randall replied 2 months ago.

Hi! My name is ***** ***** I can assist you with this. I may need some additional information from you first in order to give a complete answer.

Customer: replied 2 months ago.
Thanks Randall... we are wondering if this is some type of power saver mode, or maybe a thermostat programing issue?
Expert:  Randall replied 2 months ago.

What else do you have on? Turn the water heater to LP mode and the fridge to LP mode and no other AC uses on. Don't turn them both on as the same time. Start one on "Hi Fan" and then turn to "Hi Cool" after a few minutes. Then do the second unit the same way after about 5 minutes. Let me know what happens.

Customer: replied 2 months ago.
We have done the fan only on one and then started the other.... the coach is all electric, so no lp
Expert:  Randall replied 2 months ago.

If you can't run them both on 50 amps then something is wrong. Do both of them work fine alone?

Customer: replied 2 months ago.
both work fine seperately with either off and the other on.... when both turned on they cycle between which compressor is running while both fans continue to run.
Expert:  Randall replied 2 months ago.

What is the watt output of the generator? Same problem on the shore cord?

Customer: replied 2 months ago.
Onan 8000 watt deisel
Customer: replied 2 months ago.
We have another rv just like this one but it has the small round black thermostats.... they will both run at same time.... the other rv withe the problem has touch screen rectangular thermostats
Customer: replied 2 months ago.
same problem on 50 amp shore power or genset
Expert:  Randall replied 2 months ago.

T​hat should be no problem. Some diagnosis needs to be done with an amp draw on the A/C units and a load test on the generator. It may be just a faulty breaker, but testing is the only way to really tell. It might be in the thermostat, but that would be a power issue on the DC side or perhaps some feedback from fluorescent lighting or some other feedback from the inverter.

Customer: replied 2 months ago.
Ok, thank you...
Expert:  Randall replied 2 months ago.

Any chance they wired up both of these on the same side of the load center?

Expert:  Randall replied 2 months ago.

T​hat would cause this...........

Customer: replied 2 months ago.
That could be, we will check
Expert:  Randall replied 2 months ago.

You would be looking for two 20 amp breakers on the same side of the load center instead of having one on each leg. I have a feeling that is what happened here.

Expert:  Randall replied 2 months ago.

J​ust checking back in to see if that was the problem?