Need furnace help, read a few of the threads but did not help.

I have not used my propane furnace for a long time as I have the heat pump and it is generally warm enough when we use the RV. I just did a trip to Florida and as we all know it was extremely cold in all states. The gas furnace would kick in for about a minute or two then fail. Tried it several times same reaction. Outside temp was below freezing, about 28 or so.
After a very cold night we took it into Camping World. They told me that the thermostat just needed to be reset, told me it was like a computer and needed a reboot. They cleaned the heater for me as well, it ran for about an hour putting out great heat. The tech showed me where the fuse was and told me to just take it out for about 10 seconds and then put it back. Mind you it was daytime and the temp was around 60.
Next day we are in Florida so the gas furnace was not used as heat pump was able to keep it warm at night.
On the way back it was very cold again, the gas furnace kicks in, heats up and runs for about 5 to 10 minutes then shuts down, better than before but it doesnt run long enough to heat up the coach  and wont come back on unless I flip the switch off and on. It fires right up, puts out heat for 5 to 10 minutes and shuts off again.
I reset the thermostat a number of times but that doesn't seem to help.
I have had all 3 burners on my cook top going at the same time to make sure the gas is flowing properly, gas water heater works properly.
I think it may be a bad thermostat, has anyone else had a similar problem? I read in the forums were heaters would try to start then fail but mine actually starts and puts out heat, it just wont keep going more than 10 minutes or so then wont come back on unless turned on manually.
Thanks for reading my post.
George

   
   

Sounds like a bad upper temp limit switch.

What model????
I am up to my ears on mine, so if you have a similar model and a volt meter I could give you a couple things to try.

Please review my Furnace Troubleshooting article in the RVForum Library. It is based on an Atwood DSI furnace, but the Suburban DSI furnace is essentially identical.
http://www.rvforum.net/miscfiles/Furnace_Trouble-2.pdf

Very good info. THANKS GARY! 8)

Thank you for the advise and suggestions, I was unable to get on the internet yesterday. It warmed up to about 50F here and the heater works great again, had it running for hours. The thermostat does seem off by a few degrees but other than that no issues.
Just wont keep running very long when it is below freezing temp, I read somewhere it could be that I bought my gas in a southern state and it is mixed with something that does not operate well in the cold. But my tank is about 3/4 full so I'll have to burn that off somehow before I can try that theory. Only thing that bothers me about that is why does it run and heat with no issue then decide to stop and not restart? Or it is the thermostat, I have one of those Coleman Tru Air that controls both heaters and switches between the two depending on the heat needed and the temp difference. I was told that it was the thermostat that caused my original problem.   
Thanks again, oh and by the way it is a Suburban gas heater.

rv george' I have had similar problem with a propane torpedo heater in New England. I would position the 20# tank in the heat coming out of the torpedo heater, Not directly in front of it but close to the heat. Maybe a halogen or a couple of incandescent work lights directly under the built in tank would make a difference?

Bill

driftless shifter said:

rv george' I have had similar problem with a propane torpedo heater in New England. I would position the 20# tank in the heat coming out of the torpedo heater, Not directly in front of it but close to the heat. Maybe a halogen or a couple of incandescent work lights directly under the built in tank would make a difference?

Bill

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I think what you're saying is to warm up my propane tank a bit to see if it is indeed a bad propane mix from the southern states that is causing the problem? 

Ok last night was below freezing so I took an electric heater out to the RV and placed it near the thermostat sensor, I warmed it up to make the thermostat think it was 55F inside temp.
I then turned on the gas furnace and it ran all night heating up the RV to 71F.
So this is a first for me, if the thermostat senses it is freezing or below it wont let the gas heater run more than a few minutes, if it thinks it is the 50's it will let the furnace run as long as it needs to get the temp up to the desired temp and then keep coming on as needed.
I'm sure if I contact Coleman and tell them this they will think I'm crazy. 

It's conceivable the circuit board in the thermostat is sensitive to extreme cold and fails when cold enough inside the coach.

You mentioned you have heat pumps, so it is likely you have a controller module (sometimes called a zone controller) between the thermostat and the a/c & furnace. It is usually located with the heat pump. The problem may be there rather than in the thermostat wall unit.

Thx Gary, think I'll take it in to my dealer at some point this winter and have them check it over now that I have narrowed down the problem, I don't want to spend a hundred plus dollars on a thermostat and sensor to find out they were not the problem.
Thx to all that responded as well. I will post the outcome as soon as I know for sure what is wrong.

Is it possible that your propane tank is overfull?  I have no auto shutoff on the tanks fill so from time to time the tank gets filled to the point that the furnace will run for a short time then the flame goes out.  Flame can be restarted by turning thermostat all the way down then back up to say 65 deg.  Have to keep doing this until the propane level in the tank comes down enough that the furnace will stay lit.  Best if this happens only when outside temp remains low.

One problem that might happen, though in this specific case I doubt it, is what is in the tank.. A fairly common practice in the south, epically in the summer, is to cheat the customer by substutiting lower cost BUTANE for the Propane you are paying for,  Butane gives off very slightly more heat as I recall so the customer rarely complains, BUT, and this is the big BUT, the vapor pressure of Butane is rather close to the freezing point of water (0C or 32F) where as the vapor point for propane is somewhat closer to the temp at which you do not need to ask C or F (-40 on both scales).

However the O/P had all 3 burners on the stove going, which argues for propane in the tank.

Sometimes you can get oil or other moisture inside the regulator and that can freeze.

Diagonstic, a 100 watt standard light blub in the propane bay, positioned so it is under the regulator but not touching anythign (Trouble light works well).

John From Detroit said:

One problem that might happen, though in this specific case I doubt it, is what is in the tank.. A fairly common practice in the south, epically in the summer, is to cheat the customer by substutiting lower cost BUTANE for the Propane you are paying for,  Butane gives off very slightly more heat as I recall so the customer rarely complains, BUT, and this is the big BUT, the vapor pressure of Butane is rather close to the freezing point of water (0C or 32F) where as the vapor point for propane is somewhat closer to the temp at which you do not need to ask C or F (-40 on both scales).

However the O/P had all 3 burners on the stove going, which argues for propane in the tank.

Sometimes you can get oil or other moisture inside the regulator and that can freeze.

Diagonstic, a 100 watt standard light blub in the propane bay, positioned so it is under the regulator but not touching anythign (Trouble light works well).

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We had this same issue earlier this year when our coach was new.  We left Florida in late February after having the propane tank filled in Ft. Myers.  We stopped a few days later near Baton Rouge LA for the night.  It got very cold that night (around 28 F).  It was too cold for the electric heat pumps to be of any use, and both propane furnaces stopped running as it got down to around freezing outside.  There was a stiff wind blowing that night against the side of the coach where our propane tank is mounted, and I suspected that it was just too cold for the propane to vaporize.  I was not aware that butane was ever mixed with propane, but that could have been our issue as well.  We only had our little electric fireplace heater for heat, and it was a COLD night in the coach.

Just for the record, the fuel is Liquified Petroleum (LP) Gas, not pure "propane". It's a blend by its very definition. Several hydrocarbon gases can be used in LPG, but propane and butane are the most common.  In warmer regions the blend usually has a higher percentage of butane because the vapor characteristics are better at higher temps. Butane has a higher boiling point than propane, so it does not vaporize as well at low temperatures (below about 30 F.).

If you have problems when moving from a warmer region to a cold one, have the LP tanks topped off in the colder area. The LP dispensed will have a greater percentage of propane and that will raise the propane content in your tanks as well. Basically you would be blending your own. As little as 10% more propane makes a difference.

Thank you to all for your input, it has been a very cold winter and I have had my motorhome in storage.  I did buy a new thermostat for it and that did not work. I finally had time to take it in for repairs, figured I better do it before it gets too warm.  I explained everything to the local Winnebago dealer as best I could, they called me a few days later and told me it was fixed. I asked them what they did, he said they simply cleaned the heater, blew it out or something. They ran it for 2 hours and all is ok.
I was a little perturbed and reminded him that when I booked it in I told him that I already paid Camping World to clean it out and they too thought they fixed it but it still did the same thing, shut off when it was too cold.
Anyway I asked them to run the heater all night that night because it was supposed to go below freezing and sure enough they alled me in the morning and said it ran all night. Still skeptical I brought it home and we have had 2 very cold nights below freezing temp?s and it has ran all night both nights.
I think I will look on line to see if there is a video on how to clean the heater, obviously I can?t do any worse than Camping World tech?s. 
All it needed was a proper cleaning.  Thank you Camping World. LOL  NOT!

spoke to soon, it worked fine 3 nights but then I decided to try it again before I took it back to where I store it. It did not run all night, tried again the next night and it did run all night, confused I tried again the 3rd night it it not run all night.
All nights were below freezing temps, as well the propane was getting low from all this testing so it was refilled up here in cold country.
Once it shuts off it stays off, the only way to run it is to turn the switch off and on again, Not much wind where it has been parked, wasn't windy and it is sheltered (someone mentioned the wind may be blowing it out).
Dealer is scratching his head. LOL Guess I'll have to start carrying good electric heaters with me. 

In future, rather than not use something on your rv for a long time, you might want to consider including it as part of your regular maintenance to operate it and maintain it, in particular as part of your pre-trip preparation routine. There is real value in using these spring and winter checklists, and maintenance schedules.

Once it shuts off it stays off, the only way to run it is to turn the switch off and on again

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Completely Normal!!! These furnaces are arranged so that if ignition does not occur within 3 attempts (listen for the snapping sound), then it locks itself out. You have to turn it off (ie remove the demand for heat at the thermostat) and turn it back on to repeat the start-up sequence!!

It does this to avoid the big boom that would associated with  accumulated propane that otherwise might occur ....

RodgerS said:

In future, rather than not use something on your rv for a long time, you might want to consider including it as part of your regular maintenance to operate it and maintain it, in particular as part of your pre-trip preparation routine. There is real value in using these spring and winter checklists, and maintenance schedules.

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Yes you are so right, I do check most everything, adding the propane heater to the check list for a longer test for sure,  once I figure out why it is working and not working when it feels like it. I did turn it on briefly when I was going through checking evrything before my last trip in the fall, I just didnt run for more than a few minutes, it kicked in and heat came out so I turned back off, as well I put in a clean filter.