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Cato1966 · 09-25-2022, 11:53 AM

We have a 2005 Diplomat with both A/C units up sized to 15k btu and a new 10 button thermostat all up graded last year following a lightning strike at the park we were staying at. We replaced the 13 btu units and the 5 button thermostat.

This system has worked well until Monday when we were packing up to come home. I forgot to shut down the A/C units before I cranked the generator to let it warm up. The generator picked up the power drawn by the units immediately although my transfer switch has a built in delay board. My rear A/C came back on as well as every thing else that I have noticed. The front A/C did not restart and we had an E7 code showing on the thermostat for the front front zone.

I found only 41 volts coming out of the breaker box so I replaced the breaker with a new and checked to verify I now have 120 volts at the breaker out put. I check the 12 volt DC fuse and GFI outlets. I then reset the 10 button thermostat and still get the E7 code. The rear unit works properly so I thing the 12 DC is Ok. If I am not mistaken the DC power board works both units.

I pulled the inside the ceiling vent/cover on the front unit and double checked, found no 120 volt power. Now I am lost as to where I am loosing power. Any input as to where to check next would be appreciated.

Cato1966 · 09-25-2022, 02:39 PM

After searching the forum for a wiring diagram, I found a link to a 2006 diplomat, thank you posting that Bob.

It appears I have lost my voltage at relay #1 on my Intellitec Model 760, EMS controler board. I switched the wiring from relay #1 and relay #3 and the voltage lost stayed with relay #1. Individually each unit will run when connected to #3.

I ordered a new EMS MODEL 760 00-00894-200 off Amazon. I will post an update when I install it.

Cato1966 · 09-29-2022, 07:54 PM

Just installed the new EMS control board and both A/C units work properly now.

The control boards looked good visually so I took the relay board off of the plastic holder and found both #1 and #3 relays had a charred solder joints at the board connection.

RamiDav · 09-30-2022, 08:34 AM

Quote:

Originally Posted by Cato1966

Just installed the new EMS control board and both A/C units work properly now.

The control boards looked good visually so I took the relay board off of the plastic holder and found both #1 and #3 relays had a charred solder joints at the board connection.

Great post, I would hang onto that old board. Resoldering those
joints might be all it needs. However, new relays would be my choice.

vito.a · 09-30-2022, 11:12 AM

Great job!

YC1 · 09-30-2022, 12:34 PM

Glad you fixed it so quickly.

If your breaker panel is inside a closet with no room for air to cool the panel there are a couple of suggestions in really hot weather.

If your breaker panel is installed in a closet and above the water heater it really gets a double whammy.

My EMS board went up in flames. Fortunately it self extinguished. My panel runs cool to the touch these days after a couple of simple mods.