Rv furnace!

[DLue]

Help! My rv furnace all of a sudden only blows cold air. So the furnace is not lighting, and it continues to just blow cold air and never shuts off even if I turn off the thermostat. I either must pull the fuse or turn it off at the reset button to make it stop. Yes I have plenty of propane and other gas appliances work fine. Help!

 

[JayArr]

Make and model of the heater?

If you disconnect the gas line can you smell gas?

Any fuses burned on the circuit board?

Does the sail switch have continuity when the fan blows?

Have you downloaded the manual yet?

 

[DLue]

Help! My rv furnace all of a sudden only blows cold air. So the furnace is not lighting, and it continues to just blow cold air and never shuts off even if I turn off the thermostat. I either must pull the fuse or turn it off at the reset button to make it stop. Yes I have plenty of propane and other gas appliances work fine. Help!

Make and model of the heater?

If you disconnect the gas line can you smell gas?

Any fuses burned on the circuit board?

Does the sail switch have continuity when the fan blows?

Have you downloaded the manual yet?

Atwood heater
If I unhook the tank u can smell it for a second
I can check the continuity
And I have the original manual

 

[Kirk]

The furnace is designed such that the blower starts and moves both inside air and also combustion air with either end of the same motor. When heat is called for the blower starts and runs for 30 seconds, then the propane valve opens and the ignition fires to light it. The ignitor also has a heat sensor to know if the propane is burning and if not it will try 3 times and if still no heat is detected it will close the propane supply and turn off the ignition. The blower on some models does not stop until the furnace is turned off to reset the control circuits. Atwood has made several different models of furnace over the years so I'll have to guess which one you have, but they all operate in similar manner so this service manual should be helpful even if not the same model. By reset button, do you mean the breaker that is inside of the access cover of the furnace?

 

[DLue]

I reset the furnace at the unit, also removed the fuse and reinserted

 

[uchu]

There are good tips and info in this old post:

Atwood furnace wont light

I have an Atwood furnace that will not light. It does attempt too and there is spark present at the electrode. Just wondering if someone can explain how to check the gas valve or what they think the next step for me to take is. Thanks in advance

www.rvforum.net

 

[namumac1]

Replace the sail switch they're cheap enough. My furnace wouldn't light and that was the culprit.

 

[John From Detroit]

Replace the sail switch they're cheap enough. My furnace wouldn't light and that was the culprit.

NO. not the sail switch "There is spark at the electrod" that does not happen till the sail switch sails closed.
IF it's not lighting at all (Mine lit and went out 3 times before it gave up) the suspect list is very short.

1: NO propane/tank valve closed (Do other propane things, water heater, Stove, Work, if so not this problem)
2: Bad Solenoid More on that in a second. But the quick test is listen for the CLICK . (Click good)
3: clogged orifice (Gas jet) A spider likes to nest there and clog it.

To test solenoid Step one Multi meter than cycle power to furnace if you see 12vdc the solenoid is getting power
Second a flat piece of iron or steel hold it near the solenoid magnet (like 1/8-1/4 inch off) and see if the magnet attracts it when powered up (NO replace magnet)

Then it gets tricky and I'd suggest professionals do it. The safe way is kind of involved

Remove gas jet and hook a long hose to it , The hose should loop down to toward the ground with at least 2 feet below the valve.. Fill the hose partially with water (at least a foot of water eitehr side of the low spot. Now turn on and when the sparks snap the water level in the hose should no longer be same same. there should be 11" difference in the two sides.

There are commercical devices (Mamometer?) you can use instead of the hose. .

 

[Kirk]

My rv furnace all of a sudden only blows cold air. So the furnace is not lighting, and it continues to just blow cold air and never shuts off even if I turn off the thermostat.

Do you mean by this that the furnace will start and blow warm air for a while but then suddenly the heat shuts off and the blowing air continues? Or are you telling us that when you turn the furnace on the blower will start and blow but it never attempts to light the flame, or does it try to light the flame but then goes into lockout and continues to blow cold air?

I'm not sure exactly what is happening.

 

[DLue]

Do you mean by this that the furnace will start and blow warm air for a while but then suddenly the heat shuts off and the blowing air continues? Or are you telling us that when you turn the furnace on the blower will start and blow but it never attempts to light the flame, or does it try to light the flame but then goes into lockout and continues to blow cold air?

I'm not sure exactly what is happening.

No it blows cold air never hot air and then runs continuously without stopping, worked fine two days ago

 

[DLue]

No it blows cold air never hot air and then runs continuously without stopping, worked fine two days ago

Other gas appliances work

 

[DLue]

Other gas appliances work

Now the blower will not turn on at all when it’s set to heat, only if I put the setting to fan

 

[Kirk]

What thermostat do you have? Is that where you select fan and turn the furnace on and off? It sounds like you may have a thermostat problem, or possibly two different problems.