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Heater fan comes on but no heat


Seeria

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I'm hoping someone can point me to an easy solution :) Our suburban heater has a problem where the fan will come on but no heat then it turns off after 30 seconds. To top off that, no repair man within an hour drive can see us for at least a week! A week! eek It will be 32 tonight!

 

I've tried switching out the tanks, seeing that the connection to the tank is clean and clear. Vacuumed out vents. No go so far.

 

Any pointers, urls, suggestions would be helpful!

 

 

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Hi I had this and I was lucky because it fixed itself as I was removing furnace. I am still not sure what happened but I suspect the gas valve on my furnace was stuck and so the ignition sequence would shut down. I also had the specific problem that it would time out after 30 seconds. You can go through the sites below I saved while working on this issue. There are several potential causes included the regulator on your propane takes but I would download the specific service manual for your furnace which you can most likely find at bryantrv.com Dave

 

http://www.motleyrvrepair.com/furnaces.htm

http://beamalarm.com/Documents/troubleshooting_rv_furnace_problems.html

http://www.rvforum.net/miscfiles/Furnace_Trouble-2.pdf

http://www.irv2.com/forums/f54/suburban-furnace-starts-then-shuts-off-120893.html

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Exact symptoms for me last month. SInce my furnace was relatively new, the tech figured it was the board (says they go bad all the time). The way my furnace is installed, there is no way to diagnose without removing the furnace first, so instead of having the shop bench test, I pulled it myself and tried a new board that I bought from Amazon. Then quickly bench tested myself (plugged power to my 12V car battery) and the fan kept going, so i knew that was the fix. There are definitely other possible issues, but I would start with that.

 

This youtube video (not mine) is basically what I had to do, though I pulled the furnace out with the outer casing, and removed the casing as a separate step.

 

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Also, if you can't get it fixed for now, try running an electric space heater for the time being if you are hooked up to shore power, or buy a Mr. Buddy from Walmart, and either use the small 1 lb propane tanks, or buy an extension hose + filter and use one of your 30lb tanks. I ran the extension hose out of the RV to the tank outside. Should at least be able to keep you warm while you wait. If any of your water hoses need the air from the furance to keep from freezing, I would suggest winterizing or at least trying to get warm air in those areas.

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Our suburban heater has a problem where the fan will come on but no heat then it turns off after 30 seconds.

There are several possible causes of that symptom so I'll suggest the easy things first.

 

If you are operating without shore power and depending upon the batteries, there is a pretty good chance that your battery voltage is low. Your furnace has what is called a "sail switch" that is actuated by a vane in the path of the combustion air which your blower provides. When the thermostat calls for heat, the blower turns on first, to run for a few seconds making sure that all exhaust gasses have been removed from the system and that there is fresh air to burn the propane when it turns on. That action also is supposed to move that vane which then closes the sail switch and it supplies power to the furnace circuit board, which then turns on power to the propane valve, and a second or so later is sends a voltage to the ignition probe to make a spark and ignite the propane. If the 12V supply falls below 10.5V it will not cause the blower motor to turn fast enough for the sail switch to close and the symptom will be exactly as you describe. It is normal for battery voltage to drop as the battery is discharged and at some point between 11V and 10.5V the blower will not close the sail switch.

 

If you go outside and listen next to the furnace while someone inside turns on the furnace to start it, you should hear the snap, snap, snap of the spark when it attempts to light. If you do not hear that snap then quite likely it is something preventing the sail switch from closing but if you do hear the attempts to light it means that the sail switch is closed as the spark will never happen, nor does the propane valve open if that switch fails to close.

 

Anything that reduces the movement of air though the furnace could cause that same effect. It is also possible that your spark probe is dirty or has failed. Those probes are one of the more common items to fail in a furnace and replacement is pretty easy and they are not expensive. To check your propane supply, see if the water heater operates on propane and try lighting the stove burners. If the stove burners do light and have a mostly blue flame, then it is probable that your propane supply is OK or at least good enough that some propane burning should happen. If you watch up inside of the furnace after dark, you should be able to see the spark and at least some flaring of the propane if that is there.

 

Not all Suburban furnaces have an outside access panel and most of the suggestions that I have given are much easier to do if yours has such access. Some Suburban furnaces do not have that outside access and if yours doesn't you will need to find a way to gain access to it.

 

If you are up to a little bit of trouble shooting, go online to Bryant RV website and download a copy of the Suburban service manual and then get your meter out and do some testing. The manual has a fairly helpful trouble shooting guide.

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  • 2 weeks later...

We did, thanks : ) Found no blocks or disconnects but I did find something on the chamber. See pic. The red area is pointing to a metal flap that is (or was) holding on by 4 thin points, and not sealed in anyway. This was the norm when we got it but 3 of the 4 points were snapped off so it rattled a lot. We added heat duct tape to secure it and stop the heat leak and rattle. The tape doesn't appear to be good enough because it melted. This is where all our heat is going, into the air area around the unit under the fridge. Joy!

 

(can't figure how to link a pic here so the link to my flikr is here https://www.flickr.com/photos/138782199@N08/ )

 

Also, where that smidgen of yellow is, on both sides of the chamber is a gap that is leaking a lot of heat. Any suggestions? Is it supposed to be venting heat? Not jsut a bit of warmth but blowing heat out the yellow area and of course the top where that flap is. I can't find a part for that or how to replace the flap.

Any suggestions on how to get a piece of furnace to set over that area and secure it with something that won't melt?

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