Help! Furnace Blower will not start, and ...

[Canuck2584]

2014 FR3 30D, getting prepared for a trip south leaving Monday. Fired up the Dometic furnace this morning, worked for a while then stopped. I hear a click at the furnace but the blower does not start.

Racking my brain I realized it could be the GFCI in the bathroom. So later with 120V shore power to the RV off, I visually checked the GFCI and it appeared not to be tripped. I hit the test button, the GFCI popped out but it will now not reset. Restored shore power and it will still not reset.

So now, do I not only have a working furnace, I have no power to the microwave, the main TV, no AC, and probably other plugs on this circuit. Checked all fuses located in the bedroom, all seem fine.

Tomorrow, I'll try replacing the GFCI to see if it is faulty.

Anyone have any other ideas?

Yikes!!

[ramit315]

Maybe a dumb question but was the propane turned on?

[Canuck2584]

No such thing as a dumb question in the RV world!! I've found that out the hard way (a few times).

Yes, the propane is on but I am down to a quarter tank. I wondered if it might be a pressure issue, although the stove burners appear to have plenty of propane supply. I'm going to fill the tank Sunday to see if that makes a difference.
Anyone know if a pressure issue will cause the blower not to start up?

My other issue (GFCI) has been resolved. I had a bad connection of the main power cord to the wall receptacle when running the generator. (Forehead slap!)

[tomkatb]

Getting close to your travel day!

The furnace and thermostat are 12 volt items. The trailer is 5 years old. Has the battery been replaced recently. The average new owner damages their battery and the seldom last three years. An installed battery monitor of some kind is a good plan. The batteries are a weak link.

So you need to check voltage. Sitting idle, hours after being charged it should read 12.6 to be full. 13, something is reading the charger not the battery.

If not it takes close to 48 hours to really be full.

At the first opening of our rv we always run the stove top. That shows us the gas is ok and the battery is good, battery starter. Before we try the fridge or furnace.

Fill your tank. Recharge the battery and try the furnace again today. Use the voltmeter in your pocket to test circuits.

A common problem is bug debris in the furnace. Prevents lighting. You would hear the furnace trying to light.

Modern rv’s have fuses and switches in goofy places. Not all in the fuse box!

The furnace is the biggest user in most rv’s. It is unlikely to last more than 24 hours if you run the furnace!

[Canuck2584]

Yes, batteries are 5 years old, however the furnace blower will not run when connected to shore power either. Wouldn't this eliminate the battery issue, or do the batteries still need to be well charged to ensure the proper voltage to the furnace under shore power also?

[TheWolfPaq82]

Originally Posted by Canuck2584

Yes, batteries are 5 years old, however the furnace blower will not run when connected to shore power either. Wouldn't this eliminate the battery issue, or do the batteries still need to be well charged to ensure the proper voltage to the furnace under shore power also?

I don't believe so. I may be wrong regarding your unit, but I can run my furnace on shore power only. Did it last year while winterizing. Already had battery pulled and in garage and ran furnace while I finished cleaning inside before covering the TT for winter.

[Bama Rambler]

Since you're hearing a click, that's most likely the relay pulling in. Sounds like it could be the control module or it could also be the blower motor itself. Or it could be the time delay relay if your model has that.

What is the model of your furnace?

[Flybob]

The furnace will not run on low battery so you need to check the battery voltage. The fact that the microwave and other items do not operate lead me to believe that you do not have power to the RV and your convertor is not operating. The furnace does not need 120VAC to run, but if the batteries are low and they are not charging from the convertor then the furnace will not run. Check the power at the outlet that you are plugged into. If it is GFCI protected, the GFCI in the house outlet may have tripped. Some GFCIs do not play well together and will trip. Note the GFCI function may be at the house outlet or in the house breaker box.

[Canuck2584]

Yes, I did resolve the GFCI and shore power issue, it was a loose connection. However, the furnace blower is still unresolved. I'm down to checking the battery output voltage and filling the propane tank (it's about a quarter full currently). Failing that it's probably a furnace component issue. Good luck on getting that resolved in 2 days, lol.
I hope my little ceramic heater still works!!

Thanks to everyone for the prompt responses, much appreciated!!

[tomkatb]

The secret to troubleshooting is to eliminate stuff. What is left is the problem. Easy. They used to charge $200 an hour for me to say these things.

So. Your batteries are a likely issue. Often are. If really dead, then it will possibly influence the furnace. There are thousands of different rv’s. Many options.

Critical. Measure voltage if unknown. Measure voltage after plugging in.

Recharge batteries if necessary and evaluate replacement as yours are beyond the expected life unless you own a fancy built in voltmeter and are sure they have not had several damaging discharges. 6 volt batteries are more durable than 12’s.

This tells you the batteries are ok and tests the converter.

With the current information there are a lot of possibilities.

[Canuck2584]

BTW, it's a Suburban furnace, not a Dometic as I stated earlier, not sure of the model though.

[Flybob]

If the converter was not working due to the loose connection, you may have drained the old batteries too far for the furnace to run. Charge the batteries then try again ( it will take a few hours ). If you are depending on the heat for this trip you may consider getting new batteries as 5yrs is about the best average life.

[Lee Pedrick]

Sounds like you dont have shore power

[nutdriver]

I had a similar experience on a trip in September into Wyoming on my Suburban furnace. I definitely needed the furnace with temperatures close to freezing. I found a reset toggle switch on the furnace that got it going. The switch is pictured below just above where the blue and red wires enter the furnace assembly. I am still not sure why it failed in the first place. I happened to be on shore power so the converter was operating. I am sure my battery is not in great shape however.

[Harkerr]

You can usually find A step by step troubleshooting guide for you furnace on line at the manufacturer web site. Then check by model number. Should help.

[Larry-NC]

Originally Posted by Canuck2584

BTW, it's a Suburban furnace, not a Dometic as I stated earlier, not sure of the model though.

Oh. That makes a BIG difference! Lots of us are familiar with them. Although there are several model numbers, they all work the same.

0) You did change the little switch from Off to Heat, right? Turn it back to Off, then Heat again which resets a fault condition on the furnace control board.

1) Did you check the fuse in the distribution panel? It's a 12v automotive fuse, not a circuit breaker.

2) If the fuse is good, check at the furnace. Take off the grille. There are four wires going to the furnace:
+12 Vdc
+Ground (with respect to +12)
and two wire which run to the thermostat. If these two wires are connected, the furnace will run.

See if you can identify which wires are which and check for +12.

Do you have the mechanical, simple, bug-free thermostat, or one of those flakey digital thermostats. If digital, read the manual on how to reboot it.

[Canuck2584]

Thanks for the info Larry-NC. Regarding (0), which switch are you referring to? There is an On/Off switch behind the panel right beside the blower motor, is that what you are referring to?

[Larry-NC]

Originally Posted by Canuck2584

Thanks for the info Larry-NC. Regarding (0), which switch are you referring to? There is an On/Off switch behind the panel right beside the blower motor, is that what you are referring to?

To reset the "lockout" state of the furnace you simply have to drop the 12v to it. It doesn't matter if you remove/replace the fuse in the fuse panel, turn the Heat/Off/Cool switch on the thermostat to Off, then back to Heat, or some other means. I'm not familiar with the switch you describe.

[Bentspoon]

I had a similar problem recently and it was/is a flaky sail switch. This checks for airflow and will not allow ignition until it senses that the blower is working, then there is the time delay to clean out contaminates and then it gets lit. Now in my case it prevented the fan from starting since it was in a hosed state. A clever gentlemen suggested I pound firmly on the outside furnace cover a couple of times for a possible quick fix. I could not believe it worked. But you have to reset the thermostat. it will lock-out when there are issues, so be sure to turn it off, then pound on the door and then fire it up again. Worked twice for me - YES, I need to replace the sail switch.

Bentspoon

[Canuck2584]

An update on my furnace issue. Was able to get a mobile RV tech out to have a look. Took him 10 minutes to isolate it down to a circuit board issue. Pulled the board out (not an easy task) and you could see a couple of burn marks on the board. He figures it was the time delay relay. My extended warranty company authorized an aftermarket replacement (Dinosaur Electronics) and the furnace is back up and running. Between the deductible and an on-site service charge that the insurance company apparently does not cover, I had to fork out 2/3rd's of the cost. But we have heat again!!
Thanks again for all those that provided feedback!