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I’ve owned this unit for about a year and I can’t figure out how to turn the furnace on. I’ve gone as far as testing the furnace power. 
There is no thermostat to run the furnace anywhere, only a “system heat” Button. Ive only Ran the heat pumps in the ac units, I’ve never figured out how the furnace turns on. The thermostat for ac is dual zone and does not switch to a furnace mode. Am I missing something?

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If you have the Dometic Comfort Control Center (CCC) thermostat, the Mode button should cycle between off/ac/heat pump/furnace.

If “furnace” isn’t showing up, you may not have power to the furnace (blown fuse, bad connection), or there might be a loose connection in the control wiring somewhere. 

The ccc connects to a control box in the front AC, which then has connections to you furnace.  (See wiring diagram below). 

The first thing to try is check fuses (I’m sure you’ve done that). Next, remove the thermostat and unplug the phone wire to the thermostat and clean the contacts. For troubleshooting purposes, a pencil eraser will work for that. Next would be the contacts in the front AC. After that start checking wiring to the furnace. 
Hope this helps. 
 

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The "System Heat" switch is for a 12V powered 300W electric heater in the wet bay to keep the water tank from freezing and, depending on the plumbing, will keep black and gray tanks from freezing also.  There's an thermo switch in the wet bay that controls it.  It will come on somewhere around 40F and switch off around (???).  Keep in mind that heater draws 25A so if you're boondocking it'll suck the batteries down pretty quick. 

As for the other issue, make sure your DuoTherm is in zone 1 and switch through the different modes.  One will be furnace then just run the temp up.  Make sure your propane is on (my propane switch is in the propane access door and "up" is the off position.  Kinda backwards (like many other Monaco switches). 

- bob

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If you don’t see “furnace” on your thermostat display, it could be that the DIP switch for “furnace” is not turned on in your rooftop AC control box. That was my problem. I took off the AC cover (on roof), opened up the control box and flicked the DIP switch marked “furnace” and viola, it now appears on the thermostat menu. 

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My friend with a 2017 Bay Star swore to me that his rig had no furnace. The option was not available on his thermostat... just A/C, heat pump or fan... yet the furnace exhaust was evident on the side of his rig. When we opened the access panel ...there was his propane furnace. Between his owner's manual and Google, we determined that the furnace option on the thermostat needed to be activated via a dip switch on the panel inside the A/C cover on the roof. His dealer set it for him, and said the A/C - heat pump had been replaced before the rig was sold, and the tech forgot to set the dip switch properly. 

It's worth a look!

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