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RVing message boards => Trailers & Fifthwheels => Topic started by: Cooper AK on March 23, 2016, 02:08:41 PM

Title: Furnace blower not working
Post by: Cooper AK on March 23, 2016, 02:08:41 PM
Hi everyone,
The blower on my suburban furnace is not coming on. Consequently, I have no heat. It's March and I'm in Alaska so it's a little chilly!
When I activate the furnace at the digital thermostat I can hear it "click" as normal but the blower does not come on. The fan and A/C have the same controller as the furnace. They both work fine. I have checked all fuses (that I know of) and all appear to be in working order. Now I am at a loss.
Oh, I do have propane and the stove is working if that helps.
Any ideas???
Thanks! 
Title: Re: Furnace blower not working
Post by: Alfa38User on March 24, 2016, 10:17:23 AM
You can remove the cover from the thermostat, select heat and with a voltmeter check and see if 12V is placed on the lead  to the furnace after you  hear the click. If no 12V is present, try placing a jumper from 12V+ to that particular wire to the furnace and see if that starts the furnace. (the thermostat runs on 12V).

Make and model of both the furnace and the thermostat  might help with further diagnosis. (On some Coleman Mach thermostats, there are two sets of wires from the thermostat, a cable of 6 leads or so (for air conditioning)  and a group of 3 leads. In the group of 3 there are 12V+ 12V- (power supply for the thermostat) and the lead to the furnace (labeled W on mine). You may have to take the thermostat off the wall and pull the wiring out a bit to identify it correctly.
Title: Re: Furnace blower not working
Post by: Cooper AK on March 24, 2016, 10:22:04 AM
Thanks for the info. I'll give it a shot this morning and see what happens.
Title: Re: Furnace blower not working
Post by: denmarc on March 24, 2016, 12:22:31 PM
Year, make, and model of RV could help too. 
Title: Re: Furnace blower not working
Post by: Cooper AK on March 24, 2016, 01:18:58 PM
It's a 2012 spring dale. 267bhssr.
I've got 13+ volts at the battery.
12+ at the thermostat IF I'm doing it correctly. That's a big if.
Tstat is a digital Dometic. Furnace is a suburban sf30fq.
Title: Re: Furnace blower not working
Post by: NickB on March 24, 2016, 02:06:22 PM
Do you have a big white door on the outside or just the little silver vent?
Title: Re: Furnace blower not working
Post by: Cooper AK on March 25, 2016, 11:16:32 AM
Just the little silver vent.
The furnace is located under the refer with enough room for one handed work. I got the furnace out after a few hours of frustrating labor. I had to remove the housing as well. The blower seems to turn easily at this point. I'm leaving town today so I wont be able to test for power or the sail switch until I get back on Tuesday. Anyone have any tips on testing these?
Title: Re: Furnace blower not working
Post by: NickB on March 25, 2016, 11:31:57 AM
10 to 1 says it's a SF-XX-F model. Pretty simple machines.

It won't be a sail switch because that's later in the system of operations. You either have a Time Delay Relay or a Module Control Board. I hope you checked for power to the furnace before you ripped it out. If not, that's the place to start. Also, it's not unheard of for the power switch on the furnace to just have been accidentally switched off.

If you have 12VDC at the fan, but it's not running, replace the motor. Good luck with getting the squirel cage off, they're difficult sometimes. Spray it down with PB Blaster a few days before if you can.
If it's a time delay relay, you want to test for power before and after the relay. Pretty good chance that it's the bad part. Cheap, easy replacement.
If it's a board with built in time delay, check for voltage at the board and if it has an on-board fuse. If it's got good power, but no voltage at the fan, then you'll need to replace the board.
Title: Re: Furnace blower not working
Post by: Hfx_Cdn on March 25, 2016, 02:45:15 PM
     Coop, like I said to you in the Virtual Campfire, this is the best place to get help.  I knew the gurus would show up and give you good specific advice.  These guys are the pros and can tell you step by step how to fix it.

Ed
Title: Re: Furnace blower not working
Post by: Cooper AK on March 26, 2016, 06:13:17 PM
Thanks Nick, I'll start checking for power as soon as I can. I'll keep you all posted.
Title: Re: Furnace blower not working
Post by: Riverc on March 27, 2016, 08:30:00 AM
Mine did the same a couple months ago,changed the circuit board that solved the problem.
Title: Re: Furnace blower not working
Post by: Gary RV_Wizard on March 27, 2016, 09:57:09 AM
Check out my article on Furnace Troubleshooting in the forum Library at http://www.rvforum.net/miscfiles/Furnace_Trouble-2.pdf (http://www.rvforum.net/miscfiles/Furnace_Trouble-2.pdf)

It's written using an Atwood as the example, but the Suburban is essentially identical in operation.

If the fan motor doesn't start running at all, odds are it is a 12v power problem to the furnace or the switch that NickB mentioned. First thing to test is the fuse and that switch.A bad motor is the next possibility. The fan motor is just about the first thing to start up and even the circuit board isn't much involved until the fan is spinning.
Title: Re: Furnace blower not working
Post by: azwinne on March 27, 2016, 09:33:33 PM
Is it blowing the fuse to the heater/fan blower?  I had a case a couple of years back where mud-dabbers got into the squirrel cage thru the exhaust vent holes and built a mud/nest.
I pulled the unit out far enough to get at it to clear out the nest. Then got some of the little screens from Camping World to screen off the input and exhaust holes.
Title: Re: Furnace blower not working
Post by: MikeNNRV on October 02, 2017, 02:46:19 PM
Is it blowing the fuse to the heater/fan blower?  I had a case a couple of years back where mud-dabbers got into the squirrel cage thru the exhaust vent holes and built a mud/nest.
I pulled the unit out far enough to get at it to clear out the nest. Then got some of the little screens from Camping World to screen off the input and exhaust holes.

My furnace would not work this morning, so I am doing some research before trying to troubleshoot this evening.  My owner's manual is about useless, but it does say not to install any screens over the furnace vent.
Why?
I can see one wasp nest and another mud dobber tube that I will clean out tonight.  The screens seem like a good, easy prevention.