I have a ‘82 Nomad travel trailer. The last couple of times we were camping the furnace will stop blowing hot air. The fan will still be running just will not be blowing hot air. What I do to remedy the issue is:I turn the thermostat to the off position. Wait a couple minutes and the fan will turn off. Turn the thermostat back to the on position and it will start blowing hot air. When it stops blowing hot air the fan will continuously run and will not turn off. It will work fine over the course of several hours. It will cycle on and off as needed to maintain a consistent temperature (Until it stops blowing hot air)Any ideas on what to check?The heater is made by Hydroflame. Model number is FA7916DF. Thank you.

Do you have the manual for the heater? It probably/must have an overtemperature safety. This is probably a thermocouple to a relay. The safety may need to be replaced. You may be able to limp by lowering the setting after some period less than that which causes the cycle to begin. Leave the lower setting, probably >5 degrees for an hour then go back to the original setting, recycle until sleep sets in then use electric heaters or blankets.

So I followed your recommendation. I set the thermostat down to a cooler temperature. The heater blew hot air all night! Going to do the same during the day today and see how it goes.If what you recommended is the solution am I pushing the heater beyond its design or is it in need of maintenance?

galaxy24 wrote:So I followed your recommendation. I set the thermostat down to a cooler temperature. The heater blew hot air all night! Going to do the same during the day today and see how it goes.If what you recommended is the solution am I pushing the heater beyond its design or is it in need of maintenance?That sounds like the thermostat! Simple thinks first. By pass the thermostat by touching the wires together. That should cause the furnace to cycle on. Let the furnace run, then disengage the wires. That should cause the furnace to shut off. If the furnace works properly, you have found your problem.

galaxy24 wrote:So I followed your recommendation. I set the thermostat down to a cooler temperature. The heater blew hot air all night! Going to do the same during the day today and see how it goes.If what you recommended is the solution am I pushing the heater beyond its design or is it in need of maintenance? I think the high temperature safety is probably at fault but simple thermostats are cheap and much easier to replace, try that first.

You do have the thermostat's fan setting set to "automatic" and not on "manual", "low", "high", etc? You may have exceeded the high limit temp of the furnace if you have registers blocked, collapse of duct work, or any other thing blocking heated air exit flow. You may also have a failing high limit switch but most I've seen fail, fial open, so the furnace will not even operate. Good luck on the furnace fix!

Furnace | Good Sam Community

Timtation
Explorer
Mar 18, 2018
Do you have the manual for the heater? It probably/must have an overtemperature safety. This is probably a thermocouple to a relay. The safety may need to be replaced. You may be able to limp by lowering the setting after some period less than that which causes the cycle to begin. Leave the lower setting, probably >5 degrees for an hour then go back to the original setting, recycle until sleep sets in then use electric heaters or blankets.
galaxy24
Explorer
Mar 18, 2018
So I followed your recommendation. I set the thermostat down to a cooler temperature. The heater blew hot air all night! Going to do the same during the day today and see how it goes.

If what you recommended is the solution am I pushing the heater beyond its design or is it in need of maintenance?
DownTheAvenue
Explorer
Mar 18, 2018
galaxy24 wrote:
So I followed your recommendation. I set the thermostat down to a cooler temperature. The heater blew hot air all night! Going to do the same during the day today and see how it goes.

If what you recommended is the solution am I pushing the heater beyond its design or is it in need of maintenance?

That sounds like the thermostat! Simple thinks first. By pass the thermostat by touching the wires together. That should cause the furnace to cycle on. Let the furnace run, then disengage the wires. That should cause the furnace to shut off. If the furnace works properly, you have found your problem.
Timtation
Explorer
Mar 18, 2018
galaxy24 wrote:
So I followed your recommendation. I set the thermostat down to a cooler temperature. The heater blew hot air all night! Going to do the same during the day today and see how it goes.

If what you recommended is the solution am I pushing the heater beyond its design or is it in need of maintenance?

I think the high temperature safety is probably at fault but simple thermostats are cheap and much easier to replace, try that first.
westend
Explorer
Mar 18, 2018
You do have the thermostat's fan setting set to "automatic" and not on "manual", "low", "high", etc?
You may have exceeded the high limit temp of the furnace if you have registers blocked, collapse of duct work, or any other thing blocking heated air exit flow. You may also have a failing high limit switch but most I've seen fail, fial open, so the furnace will not even operate.
Good luck on the furnace fix!
CavemanCharlie
Explorer III
Mar 18, 2018
I have had so many wasps build nest in the exhaust pipe in the outside of my camper furnace that it would overheat and shut down. I've never had the problem where the fan keeps running though. When mine did that is just shut down completely. The thermostat is a cheap and easy thing to try first.
rbpru
Explorer II
Mar 18, 2018
I thought the way the furnace works is; the thermostat kicks on, the flame starts, the furnace plenum heats up, the blower starts, the room warms, the thermostat kicks off, the flame shut down, the furnace plenum colds to a safe level and then fan motor turns off. So the fan blows increasingly cooler air as the plenum cools.
galaxy24
Explorer
Mar 19, 2018
I will try a new thermostat and see how that goes. A simple analog heat only thermostat will be fine. Will any do? Or is there specific ones for 12V and 110V systems?

I will take a look and see if there is an obstruction as well.

When I was able to listen to the heater cycle I would hear a tick at the thermostat, 5 seconds later the fan would turn on, 10 seconds later I would hear what sounded like a flame igniting. Of course, each time it failed it was at night while sleeping or while we were away.

I will try and run it more when I can pay attention.
CavemanCharlie
Explorer III
Mar 19, 2018
galaxy24 wrote:
I will try a new thermostat and see how that goes. A simple analog heat only thermostat will be fine. Will any do? Or is there specific ones for 12V and 110V systems?

I will take a look and see if there is an obstruction as well.

When I was able to listen to the heater cycle I would hear a tick at the thermostat, 5 seconds later the fan would turn on, 10 seconds later I would hear what sounded like a flame igniting. Of course, each time it failed it was at night while sleeping or while we were away.

I will try and run it more when I can pay attention.

There is not a specific thermostat for a TT,, any will do.
galaxy24
Explorer
Mar 20, 2018
Thank you.

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