Furnace "lockout"?

Duo-Therm by Dometic.

What kind of thermostat does it have- is it furnace only?

TheWilliamsFamily wrote:
Okay, so, thank you everyone for the help. What I ended up doing was rebuilding it myself with supplied parts from PDX RV LLC for about $60.

http://pdxrvwholesale.com/products/atwood-hydroflame-furnace-model-8940-dc-iii-tune-up-kit

I replaced the sail switch, limit switch, burner assembly and orfice, and electrode.

The furnace works great but now when the RV gets to temperature and the furnace shuts down, obviously the room temp will lower and the furnace will not turn back on. The only way I can get it to turn on is either turn the breaker off for a few seconds and turn it back on or turn the thermostat off for a few minutes then turn it back on.

Again, any help would be great.

Thanks again in advance.

Your current problem means a new Board is needed. Doug

Okay, so, thank you everyone for the help. What I ended up doing was rebuilding it myself with supplied parts from PDX RV LLC for about $60.

http://pdxrvwholesale.com/products/atwood-hydroflame-furnace-model-8940-dc-iii-tune-up-kit

I replaced the sail switch, limit switch, burner assembly and orfice, and electrode.

The furnace works great but now when the RV gets to temperature and the furnace shuts down, obviously the room temp will lower and the furnace will not turn back on. The only way I can get it to turn on is either turn the breaker off for a few seconds and turn it back on or turn the thermostat off for a few minutes then turn it back on.

Again, any help would be great.

Thanks again in advance.

While this is probably board related, I also had a similar problem on a very cold evening. My furnace would shut off after a short time. If I waited it would start then stop again after 10-15 seconds. I finally had the brilliant (ahem) idea of checking propane on the stove. It was very weak. Hmmmm, I KNEW the tanks were full. Turns out I was ready to learn my first propane vs cold weather lesson. The tanks were so cold they would not flow proper volumes of propane. From that day forward I have them wrapped in foot heater blankets and have never had an issue, even down to 10 degree temps overnight. I simply hit the switch for each blanket right before evening and that's it. Uses a surprisingly small amount of my battery amps as well.

When this happens, the FIRST thing you do is verify the LP system is ON and your range burners(all 3 or 4) are ON and have good flames. Then start the furnace, Go outside to the outside vent. When you hear the Ignition start to click, you should smell LP out of the exhaust vent IF the system is allowing LP to flow. IF you smell LP, then your burner is probably dirty or has insect nests. Also, possibly the Spark electrode is not gapped correctly for a hot spark. IF you smell NO LP, then you will need to pull the furnace to determine if it is a gas valve or a electrical issue at the valve or the LP burner orifice is clogged. Doug

Out of propane?

allen8106 wrote:

3 tons wrote:

TheWilliamsFamily wrote:
Hello all. It is starting to get cold at night in Texas and my furnace is giving me grief. When I turn the thermostat up the blower turns on, the igniter sparks up it runs for 20 to 40 seconds and shuts down. I have checked the fuse and cleaned all the connections. Blew the whole thing out with compressed air. Made sure the vents were open and uncovered and register was unblocked. I'm sure it's a more technical issue but I'm hoping to fix it myself rather then take in for service. Any help would be great.

It is a Atwood Hydro Flame 8940 111

Is furnace in a RV or home??.... If either, the brand and model is always the best place to start...

OP states its an Atwood, I don't think Atwood makes a home furnace. Only RV furnaces.

Even posted model number ---8940

Here is service manual that includes that model (plus 7900/8500 series)
LINK to manual

3 tons wrote:

TheWilliamsFamily wrote:
Hello all. It is starting to get cold at night in Texas and my furnace is giving me grief. When I turn the thermostat up the blower turns on, the igniter sparks up it runs for 20 to 40 seconds and shuts down. I have checked the fuse and cleaned all the connections. Blew the whole thing out with compressed air. Made sure the vents were open and uncovered and register was unblocked. I'm sure it's a more technical issue but I'm hoping to fix it myself rather then take in for service. Any help would be great.

It is a Atwood Hydro Flame 8940 111

Is furnace in a RV or home??.... If either, the brand and model is always the best place to start...

OP states its an Atwood, I don't think Atwood makes a home furnace. Only RV furnaces.

Nice list and thanks for sharing