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furnace won'y light


raylen

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I had problem two weeks ago but mine would not light and blower would shut down after 30 seconds. I found these two helpful in diagnosing. Also, if you have your model number. Go to Bryant RV serives and download service manual. The serive manuals contain good trouble shooting guidance. http://beamalarm.com/Documents/troubleshooting_rv_furnace_problems.html http://www.rvforum.net/miscfiles/Furnace_Trouble-2.pdf

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Yea Jayco, what happened with mine is that I checked everything electrical, propane, connections short of having to take it out. Ended up decided to take it apart but shaking it taking it from cabinet caused to to work. Gas valve stuck??????? So far so good.

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My furnace fan runs but burner won't light. any ideas what is wrong

It would help if we knew what make and model the furnace is. Also, are you operating on shore power or from the batteries? An RV furnace will operate on 12V-dc down to about 10.5V or just a bit higher and then the fan does not run fast enough to close the sail switch, which is a safety device to be sure that you are getting enough combustion air movement for the furnace to operate safely. Some newer model furnaces will shut the blower down after a minute or so when the flame fails to ignite, but most just keep the blower running until you turn it off again. That is where the model you have would help.

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I recently had the same problem with a Suburban SF 25.

 

Turning up T stat started fan,,,,,,,,,,,,,,,,,,Fan ran and sail switch closed (0therwise gas valve wouldn't ever open) ,,,,,,,,,,,,,,,,,,Gas valve opened (you can hear that plus feel it) ,,,,,,,,,,,BUT THE FLAME DIDNT IGNITE.

 

Some circuit boards shut the fan off in such case while others don't.

 

I checked the HV ignitor transformer on the elec circuit board AND IT WAS PRODUCING A HV SPARK click click click when the gas valve opened

 

I cleaned and serviced and re adjusted the ignitor tip to within 1/8 inch over a place in the burner where there were the small gas outlet holes AND IT WORKED

 

While there were no visible to the eye cracks or carbon traces on the HV ignitor, to be safe, I bought a new one.

 

Later on furnace again failed to ignite so I installed the new HV Ignitor and its factory default location placed the HV ignitor tip over the gas outlet hole area HAS WORKED PERFECT EVER SINCE

 

MORAL OF THE STORY even if the eye shows no cracks or carbon traces on an Ignitor it orrrrrrrrrrr the HV cable might still be bad CARRY A SPARE

 

Again if troubleshooting the fan has to start,,,,,,,,,,,sail switch has to close,,,,,,,,,,,,,,the gas valve opens,,,,,,,,,,,,,,,HV ignitor transformer on board sends HV to the ceraimic/porcelain Ignitor Tip (you can hear the tick tick tick HV sparks),,,,,,,,,,,flame should light.

 

Over many years as an RV dealer when a furnace failed to light it was often (NOT always) caused by: Low Battery Voltage,,,,,,,,,,Loose/Dirty ribbon connector on board (remove and clean and reinstall),,,,,,,,,,,,,,,,,, Bad ground,,,,,,,,,,,,,Bad circuit board,,,,,,,,,,,,,Bad ignitor tip .

 

John T

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Mine runs and heats for awhile, then shuts off before reaching the set temp on the thermostat. Or, when it does reach the temp and shuts off, it will not come back on when the temp drops below the set temp. Today, I was just running the roof heat pumps(thermostat works perfectly for them) and noticed that the gas heat was also simultaneously on for quite awhile. The thermostat was set to electric heat pump only.

When I have only the gas heat on, I can smell gas outside by the intake and exhaust. But, heat is coming out the exhaust and it is lit and heating inside the coach.

I had the sail switch replaced last year. I very rarely use the gas heat (probably no more than 20 days since new).

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It might help to know the make and model of furnace and thermostat. RV furnaces all have a high temp. device on the heat exchanger that will cut off the heater if the temperature of the exchanger exceeds safe limits. That can be caused by too little air flow through your interior side of the furnace and especially the heat ducts. Crushed or blocked ducts can cause that to happen. The sail switch could cause the problem but isn't likely to open once the air movement has closed.

 

Some odor at the furnace exhaust is normal as the odor adding ingredient of propane doesn't completely burn and is blown out with the exhaust gasses. With the fire burning it isn't likely to be unburned propane.

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It might help to know the make and model of furnace and thermostat. RV furnaces all have a high temp. device on the heat exchanger that will cut off the heater if the temperature of the exchanger exceeds safe limits. That can be caused by too little air flow through your interior side of the furnace and especially the heat ducts. Crushed or blocked ducts can cause that to happen. The sail switch could cause the problem but isn't likely to open once the air movement has closed.

 

Some odor at the furnace exhaust is normal as the odor adding ingredient of propane doesn't completely burn and is blown out with the exhaust gasses. With the fire burning it isn't likely to be unburned propane.

 

It is a Suburban, but I don't know the model. I also placed screens over the exterior intake and exhaust holes last year. They were clean when I did it. I'll look for the model of the heater and thermostat. I thought it may be the regulator, but the fridge and water heater work fine. I really don't understand the gas heat running when only the electric is turned on.

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Both operating at the same time does sound like a control issue. In most systems, the signal from the thermostat goes to a circuit board in the air conditioner/heat pump and it then sends the proper signal to the right appliance. I have no experience in trouble shooting that type of system but would look at that first. You could check the signals from the thermostat with a meter to be sure that they are there and proper but you very likely have one of the models that use more than one pair of leads. Many of them use phone wire with 6 or more leads used but we need to know what thermostat you have to help much there. An example is below.

honeywell-thermostat-wiring-color-code-s

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