Kevin510 Report post Posted November 2, 2011 Hi all. I have a 1995 Holiday Rambler Endeavor. I traded our Bounder for it only a few months ago. Recently, we were about to go on a weekend trip so I did my usual inspection which included firing up the furnace. I was on battery power and it lit and ran fine. The next morning when we needed it, it would not light. We were plugged in to shore power at a park. I tried about 3 or 4 times with out any luck. We just used electric heaters the rest of the trip. About a week after we got back I finally had a chance to start looking at it and now it lights fine. We are scheduled to take another trip for New Years and am afraid that it will act up again when it is really cold. Everything is clean in the furnace and I have a full tank of LP. Any suggestions are greatly appreciated. Share this post Link to post Share on other sites
wolfe10 Report post Posted November 2, 2011 Boy, difficult to diagnose when it is not "mis-behaving". But, the number one cause of a furnace not lighting, but fan running, is inadequate air flow to close the SAIL SWITCH. And, the number one cause of inadequate air flow is low voltage which means the furnace fan is not turning fast enough to supply enough air flow. Other causes of inadequate air flow are blocked or inadequately sized air return and/or heater vents closed, ducting crushed, etc restricting air flow out of the furnace. How sure are you that battery voltage at the furnace was 12.0 VDC or more when this happened? Brett Share this post Link to post Share on other sites
hermanmullins Report post Posted November 2, 2011 Kevin, There is a unit that detects leaks and will shut off your gas supply. However if you were able to cook with gas then your valve is open. You said every thing was clean. Look in the burner tube to see if the wonderful Dirt Dobbers did their duty and built a nest inside of the tube. You might, in a well ventilated location, crack the gas line at the burner to see if you are getting gas to the burner. If you are, then it is in the burner itself. If not, it will be between the tank and the heater. Another thought, will you refrigerator work on LP? Same thought. Share this post Link to post Share on other sites
wolfe10 Report post Posted November 2, 2011 The furnace run sequence is: Thermostat signals furnace PC board to turn on the furnace. PC board tells fan to start. If adequate air flow to close sail switch, the PC board signals the propane valve to open AND the igniter to spark. If flame is detected, the thermocouple tells the PC board and the PC board keeps the furnace running. So where I recommend starting is verifying that you are getting as far as propane valve opening/igniter sparking. VERY easy-- just listen for the igniter clicking. If no clicking, you are not getting that far into the run sequence. Brett Share this post Link to post Share on other sites
hermanmullins Report post Posted November 2, 2011 Nice explanation. I reread Kevins post. He said that his furnace lit and ran on Battery. But when he was on shore power it did not. He then said it work when he got home but didn't say if he was on battery or shore power. Why or how could that make a differance? Share this post Link to post Share on other sites
wolfe10 Report post Posted November 2, 2011 Herman, Battery voltage makes a big difference on whether the fan is turning fast enough to close the sail switch. But, without more information we would just be guessing. Issues could include: Battery with bad cell, faulty or mis-programmed charger or converter, poor electrical connection anywhere between battery and furnace, etc. Do the diagnostics I outlined above. Plan "B" is to pull out your digital voltmeter and confirm voltage at battery AND at the furnace. Brett Share this post Link to post Share on other sites
Kevin510 Report post Posted November 3, 2011 Thanks for the replies guys. I will try and answer all the questions. There are no dirt dobbers anywhere in or around the furnace. The third time I checked, I was at home and on battery power. All of my coach batteries are pretty new and hold their charge although I have not actually tested them so I can not be %100 sure that they are perfect. Thanks again. Share this post Link to post Share on other sites
Kevin510 Report post Posted November 4, 2011 Ok. So I went today and tried to figure something out. I turned my battery disconnects and was on battery power. I then turned the furnace on. It fired right up. I let it run for about 15 minutes and it did great. I then turned it off and let it sit for about 15 to 20 minutes. When I turned it back on, it would not light. I tried 2 more times with no luck. I tried again with the gen. running and still no luck. There is a on off switch in the outside furnace access which was on. I turned it off and tried it again and still nothing. Turned the switch back on and still would not light. I am at a complete loss on this. I attached some pics of the furnace. Thanks again guys. I really appreciate it. PS. The fridge along with the cook top light perfectly. Share this post Link to post Share on other sites
wolfe10 Report post Posted November 4, 2011 Have you conformed 12+ VDC/same voltage as when it does run at the furnace when it fails? And exactly how far in the process does it get when not working-- do you hear the igniter and/or click of the propane solenoid? Also, many RV dealers have a tester that can test the furnace's PC board. But even before pulling it out remove the connections from the PC board and gently use an eraser to clean the contacts. Brett Share this post Link to post Share on other sites
chucknewman Report post Posted December 2, 2011 Sounds like an intermittent (defective) high limit switch or the sail switch. Easily checked with an ohm meter when in the failed mode. Generally when either the striker circuit or solenoid valve go bad, they remain so. Chuck Share this post Link to post Share on other sites
