Duotherm front ac wont start

[Vin2]

2008 monaco cayman
It has 2 rooftop ac’s and 1 furnace. It has a duotherm 5 button stat. The rear bedroom ac works great, but the front ac doesnt do anything.

From what i understand, there are “phone wires” that connect the two ac units together, and the rear ac triggers the front ac. I can hear clicking inside the front ac when the stat calls for cooling, but it doesnt do anything. I reached in and spun the blower wheel and it spins freely. I dont know where to start

 

[Arch Hoagland]

Has it always worked in the past?

 

[Vin2]

Has it always worked in the past?

I just bought the coach, so im not sure. Its never worked during my 48 hours of ownership lol

 

[Arch Hoagland]

Where are you getting your power from?

 

[Vin2]

Powered by on board genset

 

[Vin2]

Ok so i dont have line voltage at the front ac. When i go to the breaker, the front ac breaker has 115v but the wire goes into a board with a bunch of relays and i have to assume thats where my problem is.

 

[Vin2]

Pic of panel. It does a series of clicks when i power on the breaker

 

[8Muddypaws]

The most common reason for AC not starting is the start &/or run capicator(s). When mine did this it was very obvious because the capicator nuked itself. I replaced all three of them for just over $100 and about an hours work.

The clicks could be the compressor trying to start but a bad cap is not giving it the shot of juice it needs. Could be. Could be something else too.

 

[Vin2]

The most common reason for AC not starting is the start &/or run capicator(s). When mine did this it was very obvious because the capicator nuked itself. I replaced all three of them for just over $100 and about an hours work.

The clicks could be the compressor trying to start but a bad cap is not giving it the shot of juice it needs. Could be. Could be something else too.

I dont think its the cap because i dont have 115v at the unit. Something within the relays next to the breaker panel is stopping the power

 

[Kirk]

From what i understand, there are “phone wires” that connect the two ac units together, and the rear ac triggers the front ac.

Are you sure that the same thermostat controls both air conditioners? I am guessing that the thermostat you are looking at controls the furnace and front air conditioner and that the bedroom air conditioner has a separate thermostat.

The picture you posted shows the 120V circuit breakers, but we have no way to know which breaker is for what item. A picture of the thermostat could also help. When you say that you don't have 120V at the air conditioner, where did you measure that? When you turn on the circuit breaker, where is the clicking that you hear coming from?

 

[Vin2]

The system is 1 thermostat that controls 2 ac units. The zones are selectable on the stat. I have no power at the yellow romex entering the front ac system. I have power at the breaker, but the power from the breaker goes into this relay board and then never comes back out.

 

[8Muddypaws]

How many watts is your generator? Is it capable of running two AC units at the same time?

That box with the clicking relays is most likely your load control center.

I have one that will shed loads (like air conditioners) based upon how many amps it senses coming in. Sometimes it sheds one of the ACs based upon other loads, but only when I'm not plugged in to a 50A service.

Did you get any manuals with your new motorhome? I don't know anything about your specific electrical system.

I'm surprised GaryRCWizard hasn't jumped in yet.

 

[Vin2]

How many watts is your generator? Is it capable of running two AC units at the same time?

That box with the clicking relays is most likely your load control center.

I have one that will shed loads (like air conditioners) based upon how many amps it senses coming in. Sometimes it sheds one of the ACs based upon other loads, but only when I'm not plugged in to a 50A service.

Did you get any manuals with your new motorhome? I don't know anything about your specific electrical system.

I'm surprised GaryRCWizard hasn't jumped in yet.

Its a 7500 watt diesel onan. Plenty in my opinion to run both, but even when i try to run only the front ac, it doesnt work.

You are right about it being my load center. I dont know much about it or how it works, but could i just omit the load center and run the ac power directly to the breaker?

I have a manual printed on computer paper from the prior owner and out of order. I might buy a real manual.

 

[Vin2]

I am almost certain this issue is due to my ems system. The display is telling me that the front ac unit has power, but it definitely doesnt.

 

[8Muddypaws]

That looks exactly like mine. Not that that means I know what your problem is. At a guess I would say it's probably a bad relay.

One other idea! Check all of the neutral wires in your breaker box. They tend to put several of them in each lug and over time the vibration loosens them up. While you're in there check all of the other lugs as well. Tighten them really well.

Good luck with it.

 

[Vin2]

I jumped the wire for the front ac directly onto the incoming power on the EMS board and now the ac works. I would think that this is because i lost a leg and/or the ems thinks i only have 30
Amps, but the display says i have power to everything, even when i didnt.

 

[Vin2]

That looks exactly like mine. Not that that means I know what your problem is. At a guess I would say it's probably a bad relay.

One other idea! Check all of the neutral wires in your breaker box. They tend to put several of them in each lug and over time the vibration loosens them up. While you're in there check all of the other lugs as well. Tighten them really well.

Good luck with it.

I beleive its a bad relay within the ems board, however the board does not seem to be serviceable, as in i cannot remove the relay itself. From my research ive also concluded that this board no longer exists.

 

[Kirk]

I would think that this is because i lost a leg and/or the ems thinks i only have 30

If you have only one leg (L1 or L2) only, the most EMS systems will conclude that you have only 30A of power available. Could it be that the two sides of your power supply are in phase? If you measure between them it should show 240V but if they are of the same phase it will read 0V.

 

[Vin2]

If you have only one leg (L1 or L2) only, the most EMS systems will conclude that you have only 30A of power available. Could it be that the two sides of your power supply are in phase? If you measure between them it should show 240V but if they are of the same phase it will read 0V.

Is it possible for the generator to create only 1 phase?

The prior owner said he just replaced the inverter. Could it have been installed incorrectly?

 

[Kirk]

The inverter should have no involvement in the air conditioning power supply. Depending on the generator you have, it may have both L1 and L2 supplied in phase. It is very easy to find out by measuring between the two legs. Another way to test would be to connect your RV to a 50A RV power pedestal and see if both air conditioners work. If they do, then most likely your generator supplies both L1 & L2 in phase and so your EMS thinks that you have only 30A power.