Discovery: Heater does nothing!!!

[tompands]

My 1997 Discovery Has rear heater and front heater. Same as A/C units. I'm in Florida so really don't need heat here, but I was in NC 2 weeks ago and it was cold as a witches thingumabob. I fired up the rear heater and it worked VERY well,...no issues at all. Front heater was a different story. Went to turn the front on and it did nothing. Gave up and went back to my warm bedroom. Next day I opened the outside access panel and found a fairly good size dobbers nest on the fan cage. Busted the nest out and closed the panel back up, I said to my self,"I get to it when I get Home".

I've been home for 2 weeks and still haven't checked it, but getting ready to. I've read some other posts about heaters on here and they all seem to say the same things> Thermostat, sail switch, 12v's, blown fuse's<. Both my units are ATWOOD's. At what connections should there be 12v ? I'm assuming the fans would be 12v ? I just don't want to stick my 12v test light to 110, is why I'm asking. Is the whole heater system 12v? I know the heat comes from the propane but is there any 110 in the system at all? If it's all 12v, I'll go poking around all day.

[Old-Biscuit]

Atwood RV Furnace is ALL 12VDC & Propane fired

1997 will have a TDR (Timed Delay Relay) that has 12VDC from a fused source going to it constant
That same 12VDC goes to Thermostat...when thermostat closes it sends that DC to the TDR which heats a coil/allows DC to Fan Motor for Purge cycle

FAN Must run First before anything else can function...dc to gas valve/spark electrode etc

[tompands]

Originally Posted by Old-Biscuit

Atwood RV Furnace is ALL 12VDC & Propane fired

1997 will have a TDR (Timed Delay Relay) that has 12VDC from a fused source going to it constant
That same 12VDC goes to Thermostat...when thermostat closes it sends that DC to the TDR which heats a coil/allows DC to Fan Motor for Purge cycle

FAN Must run First before anything else can function...dc to gas valve/spark electrode etc

Just needed conformation.....thank You , sir.

[tompands]

Originally Posted by Old-Biscuit

Atwood RV Furnace is ALL 12VDC & Propane fired

1997 will have a TDR (Timed Delay Relay) that has 12VDC from a fused source going to it constant
That same 12VDC goes to Thermostat...when thermostat closes it sends that DC to the TDR which heats a coil/allows DC to Fan Motor for Purge cycle

FAN Must run First before anything else can function...dc to gas valve/spark electrode etc

Old Biscuit, I checked my TDR and I think it's bad. It's mounted on a shield of sorts and I jumped it by crossing 2 screw drivers and the unit came on and lit. I had power on 3 sides of it, top and right and left tabs. and no power at the bottom tab. Thats where I jumped the power to, and she fired up. Do you think that TDR is bad, or do I need to look somewhere else. It's a atwood 8535 model number.

[Old-Biscuit]

TDR.......has constant DC from fused source which passes DC to Fan Motor when DC from closed thermostat (calling for heat) goes to TDR

Got DC from Fused Source and DC from Thermostat when it closes but NO DC to Fan Motor.
*Jumper across TDR and Fan Starts.....TDR has failed

[tompands]

Received my TDR today and installed. works perfectly. Now I have heat in the front and back. It was almost 80 degrees here in Florida today. And I'm repairing a heater. one more thing off my list.