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Old 02-27-2021, 12:49 PM   #1
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Front Air-conditioner Power?

I am going to have a hard time even explaining this problem, but here goes.

My front ac/heat pump stopped working during this cold snap in Texas. The rear AC unit stopped working because of a burned out motor 3 years ago, but the front has been running fine.

No fan or anything working. Started troubleshooting and found there was no 120 volts at the unit.

The breaker is providing power, but it goes thru some board that is mounted right next to the panel. I have never touched this circuit board, and I am not sure of it's function, but it seems that all ac circuits run through this board.

Can anyone give me an education about the boards function, or why I am getting no power to the front air conditioning?
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Old 02-27-2021, 01:25 PM   #2
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You may be dealing with a load shedding system.

Do you have a panel labled Intelelect EMS or Energy Managenment System ?
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Old 02-27-2021, 01:33 PM   #3
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Not load shedding according to the EMS. Plugged in to 50 amps, and management shows no loads being shed at all.

But, is the circuit board I see the brains of the EMS? That would make sense as all circuits are running through it, and there could be a failure of some sort?
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Old 02-27-2021, 02:04 PM   #4
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The EMS (load shed) is part of the load center and yes it has a circuit board and relays. Try removing all 12v power form the coach, which should force a reset of the EMS board. Usually turning the house battery disconnect switch OFF is sufficient to do this, but if not you may have to get in and unplug the 12v wire from the EMS board.
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Old 02-27-2021, 02:20 PM   #5
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Quote:
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Not load shedding according to the EMS. Plugged in to 50 amps, and management shows no loads being shed at all.

But, is the circuit board I see the brains of the EMS? That would make sense as all circuits are running through it, and there could be a failure of some sort?
Yes.
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Old 02-27-2021, 02:26 PM   #6
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I have turned the house batteries off with the isolation switch, disconnected with the salesman switch, and removed all three connectors (there are only three total) from the circuit board.

Still no ac power at front AC.

Is it possible that power to the front AC comes from the rear AC?
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Old 02-27-2021, 06:09 PM   #7
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If you think board is bad you could swap board from other unit to confirm it's good or bad.
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Old 02-27-2021, 06:17 PM   #8
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Thanks Outbound, but that's almost the first thing I did. I used the back AC board in the front AC. That is why I was wondering if the front AC got it's power from the rear AC. I read where the boards could be swapped as long as the dip switches were changed to the front settings. I never swapped the boards, as the rear AC has failed, I just disconnected the board, and moved it to the front.

Still fighting this thing.
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Old 02-27-2021, 07:36 PM   #9
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Did you check for 120 volts after the shedding relay for that AC unit ?

Maybe swap AC 1 for AC 2.

Other common thing is thermostat. It needs 12 by power.
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Old 02-28-2021, 03:52 AM   #10
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I have 12v at the thermostat, and the furnace is working fine.

I have two relays on the circuit board, I guess one for each AC. I am not sure how to check for ac on them, but I will take a closer look.

I never thought about switching air conditioners front to back, that may be too ambitious for me until I get back home in spring.
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Old 02-28-2021, 04:42 AM   #11
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Similar incident last year. We were plugged into 30 or 50 amp shore power on one trip and I tried to turn on front air. When I slid on off button at my thermostat, it would not turn on. Very strange. I had to clear my head and think about what I was going to check next. Just for fun, I cycled the salesman switch on, and my thermostat would turn on and I started the front AC.
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Old 02-28-2021, 10:49 AM   #12
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The 120VAC from the breaker panel is going to go to the control board inside the A/C unit on the roof. Have you checked for 120VAC going into the control board?
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Old 02-28-2021, 01:31 PM   #13
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Quote:
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The 120VAC from the breaker panel is going to go to the control board inside the A/C unit on the roof. Have you checked for 120VAC going into the control board?
On my unit, 120VAC goes from the breaker, to the EMS board next to the breaker panel, then to the control board inside the AC. That lack of 120VAC at the air conditioning board is exactly where the problem is. (first post)

This seems to indicate that something on the EMS circuit board is not allowing the VAC to go to the front air conditioner.

The rear air conditioning has 120VAC.
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Old 02-28-2021, 02:47 PM   #14
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A little more info. Both the AC's get their 120VAC from a 2/14 romex cables.

These cables do not appear to connect to the EMS board, yet I think they do, just not in the form of romex. UPDATE (They were on the back of the board)

another strange thing is that the hot side of the breaker, when the breaker is off, is showing 50 volts. This has to be coming from the EMS board. The breaker for the rear ac has no voltage when the breaker is off, just as you would expect.

Any thoughts??

Oh yes, just to be sure the ac could work, I wired an extension cord directly to it and it worked.
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