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Furnace burner not igniting


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I think my furnace sail switch may be going bad. When I turn on the furnace and set the thermostat for heat, the blower motor starts running and the burner should ignite within a few seconds. But the burner does not ignite and short time later the blower shuts down. If I turn off the furnace switch at the thermostat and then turn it back on, I can repeat this process and, after several restarts, the burner ignites. This doesn’t happen every time but it is beginning to happen more often. If it is not a sticky sail switch, I guess I could have an obstruction in the vents that would restrict air flow. But since the furnace works after several restarts, I suspect the sail switch. I have an Atwood Hydro Flame 8900-III, model 2540 furnace. How difficult would it be to replace the sail switch? Could the problem be somewhere else?


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You might try disconnecting every electrical connection and insure that each is scratch tight . That includes the circuit board connections .


Once you have a tight electrical 'system' , it's much easier to pinpoint any other problem and at least one possibility will be eliminated .

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Here are some sites I found helpful when I had a similar problem. I am still not sure what happened in my case. I think my gas valve may have been stuck because the problem corrected after I bounced things around attempting to remove the furnace. My understanding is the actual replacement of parts is not difficult it just depends on how easy it is to access and remove your furnace. In my case I had to get past the water pump and water heater. By the time I finished banging around with all that work my furnace was working and has been ever since. Yours sounds more like air obstruction problem or a switch going bad. Could be the sail switch but also the main board or high limit. A problem with your propane regulator also a possibility. Find the service manual to your furnace. This site has most service manuals. Dave http://bryantrv.com/

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Doug, it is possible that the sail switch is failing as it does happen, that is one of the least common causes of this problem. I would look at several other possibilities first, especially if you plan to trouble shoot by changing parts. If you are operating on your batteries and not shore power, I would check the voltage to the furnace first as low voltage will make the fan turn slower and can mean it fails to close the sail switch. I would also go outside and listen carefully while someone inside turns on the furnace and listen to see if you hear the snap of the ignition probe sparking to attempt to light the propane. If you hear that it means that the sail switch has closed and it could be a bad probe or low propane pressure. If you have been using the furnace regularly it probably means that you don't have anything obstructing the air flow, which would cause the sail switch not to close.


I would suggest that you start by visiting Bryant RV website and download a copy of the service manual before you do too much work. Page 12 of that manual has a schematic of the furnace that you have and page 30 has a trouble shooting chart for the symptom that you have.


BLOWER RUNS - BUT FAILS TO IGNITE Low Voltage/High Voltage ----------------------

Gas pressure incorrect--------------------------Set pressure to a minimum of 11˝ W.C. with all appliances running. (Replace regulator if not obtainable).*

Furnace grounding wires not secure --------Clean and secure grounds established*

Air intake restricted ------------------------------Clean air intake.*

12 volt polarity reversed------------------------Correct polarity*

Motor running slow------------------------------Check voltage first. If 12 VDC while running, replace motor.

Exhaust blocked ----------------------------------Clean exhaust.*

Combustion air wheel loose ------------------Reposition and tighten.

Sail switch defective or wire off --------------Reconnect wire or replace.

Limit switch defective or wire off ------------Reconnect wire or replace.

Edge connector on circuit board dirty ------Clean with pencil eraser*

Circuit Board defective --------------------------Clean plug contacts. If still defective, replace. (check on board tester when possible).

Gas valve defective ------------------------------Replace valve or valve coil, depending on problem encountered.

Main burner orifice blocked--------------------Clean main burner orifice or replace.

High tension lead wire defective--------------Replace wire

Electrode out of adjustment ------------------Adjust electrode (take care not to damage porcelain).

Electrode defective ------------------------------Replace

Obstructed burner head ------------------------Clean burner head*

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Another common problem is opening the tank valve too fast after getting one refilled, and it triggers the excess flow valve built in to the ACME nut that you screw on to the tank. There is enough flow to make a burner on your range work, but not enough to make the furnace work. You have to turn the cylinder valve off, disconnect the pigtail, then reattach the pigtail and open the valve very slowly. Several months ago, I had a pigtail fail when the valve in the nut stuck closed and no amount of jiggling would free it, and I had to replace it. No problems since.

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Doug...all suggestions for causes are correct...


Check to see if your exhaust is blocked by wasps or other critters..as suggested Ensure NO loose or corroded fittings..


Sail switch is located behind blower cover.(easy fix four screws) before you replace turn on unit ----if fails to light----tap on housing with screw driver...tap not bang...if fires off, try this a couple of times...(if works there is a good place to start). OR find your wiring diagram here..




You can check for voltage on circuit board to see if sail switch is closed...


You say burner doesn't light until after a few try's...could be bad connection on circuit board or ignition electrode (which is also the temperature sensor)...temperature sensor is a little more difficult...you have to remove gas connection and a few wires....you might have to remove tail piece coming from exhaust chamber to remove the assembly.(again couple of screws)..check for proper gap or cracked temperature sensor.


Recommend getting magnetic sockets and magnet on a stick along with a flashlight....makes it less frustrating getting dropped screws out and back in..about 20-30 minutes to replace sail or electrode.


Good luck, let us know what you find.


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Another common problem is opening the tank valve too fast after getting one refilled, and it triggers the excess flow valve built in to the ACME nut that you screw on to the tank.

If the stove top lights or any other propane appliance like the water heater is working, this isn't the cause of your problem.

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Thanks for all the great info. We live full-time in this RV and use everything on a daily basis so no bird's nest. We are currently staying at an RV resort with good power - no boondocking on battery power. I have a Magnum 2000 inverter with a 3-stage charger which I feel would supply a cleaner 12v than a typical RV converter. My 12v supply now reads 13.3 although I have not yet taken a reading at the furnace. I haven't had any maintenance performed on this furnace during the 8 years I have owned the RV. Do any of you have periodic maintenance preformed on your furnace (or do it yourself?) How much does a RV tech typically charge for something like that?

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I've read through the documentation and am ready to begin troubleshooting the problem. So what happens? The problem goes away. Oh well, I am ready when it comes back, which will probably be the coldest morning of the season.


I opened the exterior furnace cover and and everything is easy to see and access is available to most components (except the sail switch.) The circuit board has a diagnostic LED that flashes from 1 to 5 times if the furnace fails to ignite, giving some indication of the nature of the problem.

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