No Heat! furnace not working

[RVFun4Us]

Our furnace in our 3055 has stopped working. We picked up the coach from storage and are now sitting in a State Park in freezing weather, it's dark and we have no heat. We had no problems with it previously, it's only been about 6 weeks since we last used it.
We turn on the thermostat... Furance and blower appear to be working fine. We are basically blowing ice cold air..literally. We did switch propane tanks.. we do have propane as the stove burners ignite and work fine. We read thru the Suburban & Heartland manuals and ran thru their steps to see if we can get the heat to kick in. Of course none of them worked. WE did find the 'switch' on the furnace itself and it is on. We can hear the furnace attempting to ignite but it just isn't igniting. Any suggestions?? Please!
We do have a fireplace and an auxilliary heater so at least we are beginning to warm up. The coach was 32 degrees when we picked it up and is now a balmy (??) 66.

 

[RVFun4Us]

Wouldn't you know it.. the moment I posted this the furnace managed to ignite and we now have heavenly warm air come from the registers!! We have been working on this for several hours doing the same things repeatedly. But after many times of purging the system it finally worked.
We really don't want this to happen again!! Does anyone have any ideas on what could have caused this??

 

[lwmcguir]

You might have a very small leak in the LP line allowing a bit of air to enter the system when the tanks are valved shut. Usually purging by igniting and burning the cook stove a few minutes clears this out. The other item is to be sure and open the valves on the LP tank very slowly. If the flow valve closes, it may still let you light the burner on the stove but not supply enough pressure for the heater to light. You probably have over 12.5 volts if you are hooked up as that is required as well. Curious to see what other post. Merry Christmas

 

[Rickhansen]

While there are many possibilities that could cause the furnace ignition to be intermittent, I'd be suspect of the airflow switch. These furnaces are "forced induction" meaning that there is a fan that supplies air to the combustion chamber and pushes exhaust out. It is the same fan motor the moves the air through the heat exchanger inside the coach. Airflow is proven on the combustion side with a differential pressure switch across the blower. If there is not enough difference in pressure (combustion airflow) the gas valve will not energize.

The first things to check are: Make sure all of your vents inside ar open and clear of obstruction, as there is one blower motor spinning both blowers; and make sure sure that the intake and exhaust ports outside your coach are free of any restrictions.

There are many other potential causes of intermittent ignition, such as moisture or condensation, or spiders in the gas train or differential pressure tubes that prevent the switch from "feeling" the pressure across the combustion blower.

I'm glad you got your furnace working. Hopefully it continue to work well and you won't see this problem again. Inside the furnace access door, there is a schematic. A multimeter and some basic troubleshooting skills can usually point to the problems, but the furnace is pretty difficult to work on due to limited access, not to mention they can be intimidating. It doesn't help that Murphy's Law says that the furnace will only quit when it's freezing cold and you are least equipped to fix it.

Merry Christmas.

 

[rick_debbie_gallant]

Wouldn't you know it.. the moment I posted this the furnace managed to ignite and we now have heavenly warm air come from the registers!! We have been working on this for several hours doing the same things repeatedly. But after many times of purging the system it finally worked.
We really don't want this to happen again!! Does anyone have any ideas on what could have caused this??

Maybe Santa will drop a new BigHorn under your tree tonight!

 

[RVFun4Us]

OK, the furnace was working this morning but was periodically making excess noise heard from both inside and outside. Not loud but you could tell there was a surge in noise coming from the furnace. The heat was still coming out but the noise concerns us. Then later in the morning, the ignition system did not work again. So we will try the purge again and see if that works again. Sounds like a mobile RV tech is in our future. By the way, there is no obstruction in the intake or exhaust tubes. Any other ideas would help before we call for outside help. Thanks

 

[DougLynne]

I'm wondering if somehow yu have moisture in your tanks. I've always been told to make sure my tanks are full prior to storage in the winter as condensation can get into the tanks. Not sure how but this is what I have been told. Hope your problem gets solved quickly.../Doug

 

[lwmcguir]

If the noise is from the burner it is usually due to fuel/air flow issues. If the flame lights out away from the burner just a small amount it makes kind of a roaring sound. Very disconcerting but doesn't seem to hurt anything. Obviously there is a problem. It will be quite interesting for everyone to hear the final resolution. Good luck.

 

[kbsplus2]

If it has what is called a sail switch, it then has a micro switch that puts the 12V to the gas valve circuit. The last one I worked on did not have a pressure differential switch but had the sail switch with a micro switch and sometimes they can be finicky. To work on this one I had to remove from the coach to get access panels off to get to the switch. If that isn't the problem the next in line is a snap switch which is a safety. Most are made of a bi-metal that when it overheats opens the circuit so power won't go to the igniter or the gas valve. If it is making it to the igniter and gas valve and you are hearing a funny noise in the way it is burning I would suggest a new gas pressure regulator. The stove may appear to work fine and everything but if the burner isn't burning right, the flame rod won't sense a flame and it will cycle without getting you any real heat in the coach. With a manometer you could check gas pressure if there is a tap, but most likely there isn't. Again this is if it is like the one I worked on. Haven't had to work on the one in our Razor yet. Best of luck.

 

[RVFun4Us]

Update. The furnace now appears to be working. When I took off the outside panel last night, I could hear the furnace ignitor clicking, then igniting. But it only stayed lit for about five seconds, then would go out. Did this about four times then timed out. Ran through another sequence and it finally stayed lit. I am thinking maybe a gas/air mixture problem occurred or maybe condensation in the LP tanks. Will continue to run and see if the problem is recurring. We have another six nights here with at or below freezing temps so will have plenty of opportunity to check it out. Any other ideas appreciated. Merry Christmas to everyone on the Heartland Board.

 

[jmaguire]

Sounds like a flame sensor. When the gas ignites it has seconds (usually 5-15) to "prove" flame. If it doesn't recognize the flame it shuts down. It will retry several times and then lock itself out. Many times the flame sensor can be cleaned. Use a green scrub pad if you can get to the sensor. It usually looks like a small metal rod and may even look clean. It sends a millivolt signal to the ground of the ignitor board. Bad grounds can also cause intermittant problems.

 

[rick_debbie_gallant]

I just assume that you have good gas flow to your stove burners by the appearance of a good solid flame that does not diminish over time. And you also have a good solid flame on your burners with all of them lit.

If not perhaps you either have icing up of your regulator or valve not turned on all of the way. (it has happened before, to me)

 

[jmaguire]

I seriously doubt you have a gas problem.

 

[rick_debbie_gallant]

I seriously doubt you have a gas problem.

Just another thought. Very easy to check. Some times it is the easy ones that will fix things.

 

[RVFun4Us]

Yes, we have good burn at the stove, all three burners. Problem is only at the furnace. Still working fine as of this evening. Problem seems to have righted itself. That is why I am thinking a condensation problem from storing it the last six weeks in above average rainfall along with cold temperatures in the Portland, Oregon area. We have never had a problem like this before from having partially filled LP tanks. We always keep one full and use the other until empty, then fill right away. Other suggested cause of a flame sensor sounds like it could be the problem except you would think it would continue to cause problems. With no issues the last day now and the furnace continuing to cycle, maybe we can rule that one out? Will keep watching and keep this board aware of any changes. Thanks everyone for your input.

 

[navyAZ1]

I have been having a very similar problem if you read my previous thread you'll see what all I have had done or have done myself. Our intermitent problem turned out to be the gas valve. The way we found our problem was once I noticed no gas smell when the furnace tried to ignite then the tech suspected the gas valve, we disconnected all the wires from the gas valve and put a ohm meter on it, the tech said it sould read 40 ohms if it is working properly it did not read that high. Our furnace had got to the point it would not ignite at all but for months prior to this it would work some and then not work at all until finally it would not ignite at all due to the gas valve finally quiting. Ours is now fixed hope you get your problem figured out.

Ron