What to Do When a Gas Furnace Won’t Light

By RV Lifestyle & Repair Editors

Question

Hi, we have a 2016 Forest River Rockwood Signature Ultra Lite fifth wheel, and I cannot for the life of me get the pilot light to relight. It’s a Suburban gas furnace. We live in South Carolina and the nearest dealer is 55 miles away. Help! Submitted via Facebook
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Answer

  Hi there, thanks for the question. This model does not actually have a “pilot light,” but rather a direct spark ignition (DSI) that ignites the flame. When the temperature get down to the specified low, the gas valve opens and LP or liquid propane flows through an orifice to the burner assembly. The spark igniter sends a spark to ignite the flame similar to a manual spark or Piezo in a residential gas grill. If your furnace is not starting, you will need to look at the following items:
    1. 1. House
battery
    power. The furnace needs at least 10.5 volts DC and sometimes more to open the valve. This must be checked at the module board with a multimeter.
    1. 2. Blown
fuse
    . There is a 12-volt fuse in the distribution center and sometimes an inline fuse in the module board on the furnace. Verify they are in working order.
    1. 3. Correct LP
pressure
    . Do the stove top and other LP appliances work correctly?
Here are some other questions and troubleshooting ideas:
    • Does the blower run, but the furnace does not light? If so, this is usually a low 12-volt issue as the blower will run under 10.5 volts
    • Do you hear the spark igniter trying to light? If you hear a clicking sound, the igniter is working but there is no gas or it has a cracked ceramic housing and is carbon cracking which means the spark is not “jumping” to the burner tube, rather following the crack to ground.
    • Another issue could be the thermostat. You can jump the wires to bypass the thermostat to see if it starts.
A lot of things to try here. Let us know if any of this works or if you have any more questions. Good luck! Safe travels, David Solberg   Related: Understanding the Fuse Panel of an RV Distribution Panel RV Battery Maintenance: Checking Battery Charge How an RV Propane Tank Pressure Regulator Works Do you have an RV repair question you’d like answered by an expert? Email your question to editor@rvrepairclub.com or reach out to us on Facebook. Please note: questions may be edited for clarity and relevance.  
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185 Responses to “What to Do When a Gas Furnace Won’t Light”

  1. Monique

    How do we get the module board out. The gas works, the stove lights and the blower works but it's blowing cold air. We have a 1991 Kountry Kamper.

  2. Ryan Prejean

    None of the igniters work in the camper unless hooked to electricity. Won’t light when running off just the battery. The battery is brand new and has been checked. Battery is not the problem. Any ideas?

  3. Grace

    I have a 2010 Coachmen Catalina with a suburban (SF-30F) gas furnace that will not light. The blower works and it will try to light 3 times before shutting off. We replaced the igniter and the circuit board with no luck. What could be the issue?

  4. sam Satterthwaite

    My brand new (in 2017) fifth wheel with a suburban furnace had a different problem that neither the local dealer nor Suburban seemed to know about. The furnace would not light above about 7,000 ft elevation. I did several test runs to verify that this was an elevation issue. The stove burners, oven and hot water heater all worked fine. The furnace DSI would click and there was enough gas pressure. Luckily, the trailer manufacturer had a service rep that had encountered this issue previously. He indicated that the spark gap needed to be increased. Neither the local dealer nor Suburban were willing to agree to widening the spark gap. Unfortunately the manufacturer was 1200 miles away and widening the gap would require removing the furnace from the trailer. I finally managed to get all parties together on a phone call where the dealer agreed to widen the gap -for a typical furnace service fee. After agreeing to pay the fee myself and requesting that the dealer record the before/after gap dimensions the dealer performed the service. The furnace has started ever since. Unfortunately, the dealer did not record the gap dimensions, nor have I purchased anything from that dealer since.

  5. Bill

    I had that problem and it turned out to be the sail switch was not working. Blowing air from furnace fan causes the sail switch to move and that tells the igniter it is ok to ignite.

  6. Bruce

    I have had box elder bug nests in the sail switch area. If the sail switch doesn't work, the igniter will not operate. Last spring on the other end of the country ours wouldn't operate. Took it to an RV repair and they put in a new circuit board. No problems since.

  7. Phil garth

    Where is the filler for the brakes on a georgy boy 3515 s reg

  8. Mike

    After checking everything mentioned above, we spent the night dressed for outdoors & had 3 blankets, 2 opened wool ponchos, & 2 furniture pads for warmth. Next morning I was mentally going through the checklist, when I reached out and lightly slapped the thermostat. The heat came on immediately! LOL! Now I start my checklist at the thermostat to make sure nothing has been shaken loose during the trip! 😄

  9. Terian

    Domestic furnace . Out side sounds like it’s trying to ignite but making a browning noise. Sounds like someone’s beating onside of camper

  10. Luis Valle

    I need to kn how to turn on heat do I just go to thermostat and turn it on or do I have to take premnilary steps. New to rv . Thank you Hello Luis, Please let us know what year/make/model your RV is and I will get this question off to the Experts. Thanks! Customer Service RV Repair Club