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Old 01-25-2022, 09:31 PM   #1
Old Mustanger
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Join Date: May 2015
Location: Rockett, TX
Posts: 441
Thermostat problem?

On our trip back from Maryland a couple of weeks ago, I got the E1 error message on the Dometic CCC 2 thermostat (loss of communication with system control boards). When I did the reset it didn't work and the display showed Zone 4 (I only have 2 zones). Needed heat so I called a mobile repairman, after messing around for about an hour he ran 2 wires out from the furnace thermostat connection and I went to Walmart to get a cheap thermostat just to enable the furnace to run.
Got home and let it alone for awhile, on a whim I did the reset procedure on the thermostat and low and behold zones 1 & 2 showed up. Returned the thermo. wires to their correct connection and the furnace works fine.
Now after all that I'm wondering if the heat pump and ACs will work, Is there a safe way to test them with only 20 AMP power available (without getting on the roof)? Maybe just adjust the thermostat to start them and turn it off immediately when hearing the start up hum?
Jerry & Debbie
with Fur Babies Sasha & Sam
2018 Alpine 3401RS
2019 Ford F350 SRW
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Old 01-26-2022, 06:34 AM   #2
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Join Date: Mar 2014
Location: Mountain Home, Idaho
Posts: 2,304
the CCC2 thermostat ( same unit I have ) controls ALL HVAC fucntions thru the CANBUS line...

This is a simple telephone cable with two wires used to provide 12 volts down the the thermostat and two wires for CAN HI and CAN LO signals...

I have had the E1 error before and when I did a reset got the same results you did with a Zone 4 showing.. which I dont have a Zone 4

The routing of that telephone line is: CCC2 up to the roof Zone 1 A/C control board, another 4 wire telephone line routed from Zone 1 Roof A/C to Zone 2 Roof A/c control board... Additionally the furnace signal wires ( two blue ) are routed from the Zone 1 control board A/C unit down to furnace control board.

To correct my issue I removed BOTH roof A/C covers and RESEATED the telephone line from thermostat to Zone 1 board, telephone line comng out of Zone 1 board to Zone 2 board and RESEATED the Zone 2 control board connection

A RESET on the CCC2 tells the thermostat to ZERO OUT ALL past learned DEVICES across the CANBUS circuit and go find them again..

A dirty or loose connection at either of the two roof A/C control boxes OR the connection on the backside of the CCC2 thermostat itself can cause the thermostat to misidentify what zones are actually out there on the CANBUS loop.

Also... You need to remove battery power and shore power to remove the 12 volts DC that is present AT ALL TIMES to the roof A/C control boxes... this will let the relays located on each control box reset as well...\

If the problem returns later on then you may want to ohm out each of those telephone CANBUS lines point to point using long jumper wire to let you connect your ohm meter and verify good continuity on the YELLOW/GREEN CANBUS Hi/Lo leads... the Red and black wires are the 12 volts DC to the thermostat and control boxes...

Also - on each roof A/C unit the control board has a set of dip switches.. these are used to tell the CANBUS if a furnace is in the loop, HP, etc... take a picture of the current dipswitch settings and cycle the dip switches ON OFF and few times then return to their original found positons...

Doing this will "wipe" the dipswitch contacts ..

A RESET must be done again on the CCC2 after cycling those dip switch settings

2007 GMC Classic club cab 4x4 Duramax LBZ
2014 Alpine 3010 RE. 34 foot fifth wheel
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