Dometic zone 1 dead

[JimM68]

My front zone seems to have come up lame. (rear zone works perfect)

This is a 5 button dometic duo-therm, controling a pair of 15k dometic a/c - heat pump units, and a pair of propane furnaces.

RV is a 2008 Monaco Knight.

Last time the front furnace was asked to work was 2 weeks ago. Bus ran out of propane, unknown if furnace was on at the time.
(is there a lockout that requires a manual reset?)

It doesn't matter what mode I select, the front zone does nothing.
Normally selecting furnace will immediately start the furnace blower, selecting a/c or heat pump will start after a 3 minute delay.

Haven't done much. Killed all power (a/c, batteries, solar, shut it down cold) for 5 minutes, powered battery up, tried to start furnaces. Rear did, front did nothing.

I checked the fuses in the back closet, there are 2 related, one labelled "a/c furnace" and one labelled "a/c furnace rear opt"
Both are good. removing the one labelled rear kills the rear furnace. removing the other kills everything, including the thermostat.

Thanks for any tips on correcting this.
It's way cold in E. TN this weekend.

[dougrainer]

tropical_ron wrote:
Do all units show up in the thermostat control? If so, cableing is most likely ok. If furnace is missing in control display, suspect disconnected rj11 control cable that diasy chains between each component; front AC, rear AC, front heatpump, rear heatpump, front furnace, rear furnace... Just our experience...After service tech forgot to plug-in one of the rj11 cables...

A Cable disconnected will NOT cause a loss of only the furnace on the display. It will cause a LOSS of all functions(display) for that Roof AC unit. There are only 2 cables on a 2-roof top system.
1. Cable from Zone 1 to the wall Tstat
2. Cable from Zone 1 to Zone 2
3. Cable from Zone 2 to Zone 3 IF you have 3 roof top units

[JimM68]

Thanks all, appreciate the help.

According to the son who is sleeping in there, the front furnace "woke up" around 3 am...
And has worked since.

Thanks again.

[tropical_ron]

Do all units show up in the thermostat control? If so, cableing is most likely ok. If furnace is missing in control display, suspect disconnected rj11 control cable that diasy chains between each component; front AC, rear AC, front heatpump, rear heatpump, front furnace, rear furnace... Just our experience...After service tech forgot to plug-in one of the rj11 cables...

[dougrainer]

Are you stating that Zone 1, ALL the various mode operations are displayed? When you toggle thru Fan/COOL/HP/Furnace, ALL will show in the display? Only the furnace uses 12 volts to run. ALL other Zone 1 operations requires 120 volts to the Front AC Zone 1. There are 2 BLUE wires at the Zone 1 control board. You should be able to drop the return AC grill from inside and find those 2 wires. They should have 12 volts on 1 wire and 12 volts on BOTH when furnace is called for. IF you have NO 12 volts on either wire, then as Chris suggested, either the CB on the furnace is tripped or the FUSE for the Furnace is tripped/Blown. There may be a separate fuse for just the front Furnace. Usually, since you removed that fuse and the tstat went DEAD, that means there may be another fuse for the front furnace. The POWER for the Zone 2 control board and tstat display comes from the FRONT Zone 1 control board. BUT, the FIRST thing is to verify those 2 blue wires for power. Doug

Your one question about lock out. The furnace will attempt 3 time to light and if you have run out of LP will indeed shut down. But, all you do is have the tstat call for another furnace cycle and it will respond. BUT, you may have to cycle that furnace 4 or more times(12 ignition cycles or more) to bleed the system of "air" since you ran it out of LP. Not really air, but lack of LP. Doug

[bdpreece]

Just a thought since I am not sure how the furnace plays into this but when one of my heat pumps failed to work I found they thermostat controls everything via what looks like a phone line. I unplugged and re connected the cables at the heat pumps and at the thermostat and everything started to work. Might be worth a shot. Not sure if the furnace gets it commands the same way.

[Chris_Bryant]

There will be a 12 volt breaker on the furnace itself- check that, particularly if the furnace is an Atwood/Hydroflame.