RV Doctor – My RV Furnace’s Gas Ignition Isn’t Working

April 13, 2010 by Gary Bunzer · 9 Comments  
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Dear Gary,
I have an Excalibur 8500-II furnace and the gas ignition has stopped working. The blower works fine but no spark to ignite gas. What could it be? - Mike Watt, (Winnipeg, MB)


Gary BunzerMike, there are a few things that may be causing this, the most likely of which is low voltage, a faulty control board, incomplete ground circuit or loose wiring.

Open the furnace access panel on the outside of the coach to gain access to the control board and wiring. Carefully unplug the wiring harness from the control board and visually inspect the plug and board contacts for damage, dirt or corrosion. If the board contacts show any sign of corrosion you can clean them minimally with a regular pencil eraser, completely with a chemical cleaner and protectant.

If there is corrosion or dirt on the plug contacts carefully scrape it off with a fine screwdriver, dental pick or similar tool. Be very careful not to bend the connectors in the plug or they won’t make proper contact with the board contact strip.

Check for voltage between the red and yellow wires with the furnace turned on. Any voltage lower than 10.5-volts DC will likely cause the system to malfunction. Check the connector wires for damage and loose connections, paying particular attention to the yellow ground wire. Securely re-connect the wiring harness to the control board and test the system again.

If it still doesn’t work, I would suspect a board problem. The board can be easily removed and taken to a qualified RV shop to have it tested.

Other possible culprits are the sail switch or limit switch. It is also possible that the blower is not reaching its rated speed or that the combustion wheel has become loose or weighted down with lint and dust. These components are relatively difficult to access and test without disassembling the furnace further or removing it from the coach.

Unfortunately, space limitations prohibit us from going deeper here. However, I’d have to place my bet on low voltage anyway.

(Please feel free to comment, however, please also note that due to the volume of communications I receive from multiple channels I cannot guarantee a personal response in every instance. However, questions of an overall general interest may be considered and published in an upcoming RV Doctor column.)

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9 Responses to “RV Doctor – My RV Furnace’s Gas Ignition Isn’t Working”

  1. Dick Boak on April 13th, 2010 8:13 pm

    I had a similar problem last week and it turned out to be mialigned igniters. They apparantly can be jiggled out of alignment by rough roads, bumping over curbs etc.

  2. Tim Tinsley on April 13th, 2010 8:59 pm

    I had a similar problem and it was to simply unplug the fuse for the furnace and plug it back in. Seems that there is a safety feature that if you run out of propane it turns it off. Might work for you..

  3. Geoffrey Pruett on April 14th, 2010 9:40 am

    One more case of do not leave home without your Digital Voltmeter! Most consistant low price is Harbor Freight, at the prices they ask do not go for the bottom of the line. Less the $40 will get one with the soft (bounce proof) case which will pay for itself on the first trip off the frame, battery box etc. Having over 50 years in the service business I still prefer analog (swinging needle) meters but they always fail the bounce test. Just remember to read only the first 3 digits unless on a special test, more just muddys the water and will lead you on a wild goose chase. Have fun!

  4. melissa on April 22nd, 2010 5:54 pm

    We have 2004 Fleetwood…All the sudden our central vac stopped working.
    anyone with same problems?

  5. wally on August 23rd, 2010 5:55 am

    I have a Duo-Therm furnace in a 34 foot citation RV.It sparks ok. but will not ignite propane.. What could be wrong ?

  6. PJ Smith on September 2nd, 2010 6:49 pm

    I have only had my 2003 Fleetwood Pace Arror DP for a year. Mostly, it is very reliable and fun to operate. I have a problem I cannot resolve, however. My two overhead A/C units only operate if I am running my generator. Two days ago while running one of the units, it suddenly shut down. The other A/C stopped working, as well. Both units work individually off 30/50 hookups but, will no longer work when I do not have an electrical hookup (i.e., driving in this Texas heat). I have read the manuals searching for clues such as circuit breaker and fuses (can’t find a 35 AMP fuse anywhere in the RV, however). Since both A/Cs work great while parked and hooked up to electricity, I can’t imagine both would have the same problem if it was a unit problem. So, I am stuck and cannot dry dock if I want A/C from any source other than the front dash air. I hope this issue makes sense…after all, I am still a rookie RVer.

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