Furnace Won't work!

[RobRV]

Help Needed!
The Temperature in this part of the World has taken a change for the worse! Winter has come early. Today I decided to test all the appliances to make sure everything was ok. I do have an electric heater running and light bulbs in strategic areas of the Coach so no frozen Pipes or Tanks.The Coach is plugged in , the batteries are fully charged.

So Today I turned on the Furnace Thermostat and nothing happened . No Lights,No LCD Display, No Fan absolutely Nothing.

I Have Checked the Fuses and Breakers I have 13.4 Volts at the Fuse. The Thermostat is a Duo Therm Unit that operates the Furnace and the AC Units. It connects via a Phone Type Plug so I can't "Cross any Wires".

It's too Cold out to pull the Exterior Cover at the Furnace but maybe there is something inside there that I need to check! I think it is a Suburban Furnace.

Any of You experienced HVAC Folks have any suggestions?

[GaryKD]

Hi RobRV,
If your coach is like mine, pull the vent type cover to expose the furnace. Remove the furnace cover. There is at least one, maybe more, fuses behind this cover.

["007"]

You have programmed the DUO -Thermostat to furnace and its off cool on zone #1.

[RobRV]

Thanks Gary ,
I'll be doing that in the Morning! It's Cold and Dark here so I will tackle it in Daylight with the Heat Gun to loosen the Goop sealing that Cover to the Side of the Rig!
I'm pretty sure there should be a circuit breaker inside there!

The Thermostat doesn't even show any display. The last time I used it everything was working!

["007"]

You need to see a display check your 12v fuses on your main 12v fuse panel maybe located next to your load center in cabinet.
Pull fuse and replug in slots. It should be marked furnace paper sticker.
The fuse's Gary is talking about are inside pull louvered vent off cabinet has Velcro holding it to cabinet opening, may see three fuses taped together inside vent inside.

[Luv2go]

Rob, on our coach there's a fuse in the wire going to the furnace that you can get to by removing the cold air intake inside the coach. You should be able to see it when you remove the intake vent (ours is about 5" x 25" and made of wood, it uses clips to hold it in and pops right out when I pull on it).

[RobRV]

I looked in there but can't locate any Fuses or Fuse Holders. I will look again! in the AM The Main Fuse is OK in fact I changed it and checked the Voltage at that location!

["007"]

Your Battery Cut Off switch is on correct?
You need 12v's for everything to operate.

[GaryKD]

Hi RobRV,
My post #2 is accomplished from the inside of the coach. My suggestion is similar to Luv2go's post.

[RobRV]

Well I finally have a partial solution to My Furnace problem. This appliance was obviously installed on a Friday by a person with a perverse sense of humor. I located the two Fuses Stuffed inside the Blower Cabinet and reachable only after removing all the Hold Down Screws inside and outside the Motor Home. In addition to the Fuses which tested OK ,there is a Relay which had become unplugged from It's socket during the manipulation of the wiring. After Plugging it back in, it seats very tightly ,so it didn't just fall out unless it wasn't plugged in properly to begin with! The Socket had apparently been screwed to the Outside Wall , then the Kitchen Plumbing was installed across the Relay.Nice going Newmar!

I hoped that with the wiring sorted out it would start right up but, No it wasn't going to be that easy. There was still no response at the Thermostat. Bugga!

I dashed into Town...Nine Miles on an Unplowed Country Road to see if I could obtain a New Thermostat. Of course the exact same model isn't available so I figured I would try installing a programmable Honeywell unit that looked to be the right size and specs. Of Course after I returned Home I discovered that the Wiring for the New One bore no resemblance to the Original.

Which lead Me to the Next Problem. The wire which plugs into the back of the original Thermostat is like a Telephone Cord with 4 Wires yet at the Furnace there are just 2 Wires entering the enclosure and they are a different type of wire entirely. So Before Hacking up the Phone Cord I decided to run a continuity test to determine which of the 2 Wires actually connected to the Thermostat, guess what No Continuity!
Hmm I wondered, if I connect the 2 thermostat leads together at the Furnace will it run.... Yes.. We have a Fan ... Ignition ...Heat Oh Yes Glorious Heat!
So Now I have to figure out where these wires go that have no continuity from the Thermostat to the Furnace. They managed to hide them somewhere inside those Kitchen Cabinets and there must be a connection Block of some sort hidden somewhere or a connecter from the Phone Cord to the 2 strand Hard wire!
Does Anyone have any ideas which panels need to be butchered or removed or am I missing a Common Bus Bar somewhere!

I have hooked up a Temporary Thermostat that will get Us past this Cold snap , but would really like to find where these Wires go so I will be able to use the AC Units when we get to Mexico in January!

["007"]

If you have AC's working off thermostat the other two leads go to control modules of the AC's.
I think the telephone cable connects to a interconnect to feed the additional AC's..

[RobRV]

That's the Thing that I can't find that Interconnect! Is it a Box of some sort Hidden away inside a cupboard or did They Bury it inside a Wall?

["007"]

This PDF, take a look at figures A-7,D-4, D-6, D-11.
You need the correct thermostat for it all to work correctly.
If cannot find the correct one you may have to change control units of AC's.
You may just have one of the multiple wires disconnected I'd look for a simple problem.

["007"]

D-34 & D-37 MAYBE SOMETHING like your setup in your coach.
If you have the furnace working now with correct DUO- THERM , PROGRAM your AC to operate in zone 1.
THE CONNECTIONS ARE IN CONTROL UNITS OF YOUR AC's.
12AM HERE will see how you made out in am.

You mentioned in one of your post's its cold and dark outside the heat pumps will not work below 40*.

HAVE ADDED IN QUICK TIPS & MODS