RV Furnace Intermittently Works

[clarkjw4]

Hey All,

New to the forum and spent a half hour or so combing through posts to try to find our specific issue. Unfortunately....no luck. I'm sorry in advance if this has been answered before and I was just unable to locate the post.

We have a 1996 Wilderness 5th wheel. We have it parked where we are going to build and currently live in it full time. We have constant power that we are hooked to and a 250 gallon propane tank.

Our heater works fine in above freezing conditions, but lately our nights have been slipping into the 20s and below and we've noticed that our pilot won't start on some cycles. I believe it is an intermittent pilot using 2 metal rods to create the spark. On a regular cycle, it will initiate, start blowing air, and within usually about 20-30 seconds the pilot will ignite. Sometimes though the pilot will not light when it is cold. We fix this by going to the thermostat and switching it to off. Wait for the blower to stop and the system to fully shutdown. Then we switch to the heat setting on the thermostat and it kicks up fine no issue. Not a pressing issue now, although it would be nice to stop waking up at 3 A.M. to slide the switch back and forth to kick start it.

The only promising answer I've found online is that condensation could be freezing in the lines....I don't see how switching the thermostat back and forth would fix this though.

Puzzled and confused,
John Clark

[clarkjw4]

Finally switched out the Time Delay Relay last weekend and no issues this week. Thank you all for the replies and guidance.

[clarkjw4]

Thank you all for the replies! We have limited internet so I apologize for the delay. Our RV furnace is an Atwood 8900-II. I am going to take it apart over Christmas and see if I can track down the culprit. Thank you all for a direction to start!

[ppine]

RV furnaces have some odd valves and systems that can get dirt in them and fail to function. Not like residential at all. When I get frustrated, I call a mobile RV tech that can go right to the problem in 10 minutes. They don't cost that much. Saves a lot of aggravation.

[chainegang]

If your furnace is the original to Motorhome and has not been changed or replaced, then it is around 24 years old. The likely suspect for the rudimentary description you gave of the symptoms gets my suspicion that the "time delay relay" is wearing out. One symptom is longer and longer periods from cold start, that is, not having run for awile. You turn the furnace on, later the blower comes on for a period, then the igniter fires up to lite the propane for furnace operation. The delay should not be a long one as it is to assure that all and any residual gas fumes are purged from the area of furnace before ignition. So long as the blower is fully operational as opposed to slow speed for lack of sufficient power, or that it cannot get up to speed and the sail switch cannot fully function. But that is a different issue from yours. This delay is all part of the operation of furnace whether cold startup or ongoing cycles. Your retriggering the thermostat is triggering the relay and shocking it to resone correctly. Eventually even that will not work. Time delay switch replacement is a simple one for installation and is not a very expensive part. Please let us know when you track down the culprit.

[enblethen]

Post make and model of the furnace.
You don't have a pilot by what you said. You have a DSI (direct spark ignition).
A lot of moisture on the porcelain electrode could be your problem. The porcelain could be cracked and spark escapes to ground and not getting to the electrode.
The high tension wire could also be the culprit if it has damaged insulation doing the same arcing to ground.