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Old 09-24-2021, 07:49 PM   #1
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Furnace fan will not run.

I have a 2016 Apex 21' trailer. Last night the furnace fan quit. anyone know which fuse runs that on our trailer? thanks
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Old 09-24-2021, 09:41 PM   #2
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fan

open main fuse panel and look for a red light ,indicates blown fuse. battery hooked up? and charged .dometic 2 way fridge. cycles ,uses 12 v also.
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Old 09-24-2021, 09:54 PM   #3
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furnace fan

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Originally Posted by Thomas ho View Post
open main fuse panel and look for a red light ,indicates blown fuse. battery hooked up? and charged .dometic 2 way fridge. cycles ,uses 12 v also.

no red lights show. Fridge runs on propane or 120. battery is hooked up. no luck still. thanks for help though.
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Old 09-28-2021, 02:04 PM   #4
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furnace fan still wont work

took camper to Camping World. they want 70.00 to diagnose fan. says its proably a fuse, but wont tell me which fuse.,,,? I cant find any blown fuse in the panel....
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Old 09-28-2021, 03:59 PM   #5
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Take the cover off the furnace and locate the fan motor and follow the wires. You should come to a relay or switch and eventually to a fuse and a power supply.
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Old 09-28-2021, 04:04 PM   #6
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Bad advice

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Originally Posted by aircommuter View Post
Take the cover off the furnace and locate the fan motor and follow the wires. You should come to a relay or switch and eventually to a fuse and a power supply.
Bad advice.

To see the fan motor of a Suburban furnace you have to do some serious disassembly--only to find out there are no fuses inside. I don't think anyone puts an inline fuse on the furnace either.
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Old 09-28-2021, 04:06 PM   #7
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Furnace my be in lock out.
Is your fuse panel labeled?
Do you have a multimeter?
If furnace is in lock out you should turn it off and remove the fuse briefly to reset it.
Check fuses with multi meter by removing one at a time and testing with the meter.
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Old 09-28-2021, 04:25 PM   #8
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The tell tale red led next to the fuse won't light up in some circumstances.
CHECK ALL FUSES WITH YOUR MULTIMETER.
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Old 09-28-2021, 04:38 PM   #9
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Quote:
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The tell tale red led next to the fuse won't light up in some circumstances.
CHECK ALL FUSES WITH YOUR MULTIMETER.
X2!
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Old 09-28-2021, 04:43 PM   #10
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Some suggestions:

1) How to check a fuse. While a red light on the panel should alert to a blown fuse, perhaps that's not working right. Don't know which fuse? Check them all. Systematically pull each fuse and shine a flashlight through it from behind. Merely eyeballing the fuse can lead to a false determination. The light shining through from behind will reliably reveal if a fuse is intact or blown.
2) Are you sure the battery is good? Do your lights work? Does the overhead vent fan work? If you have a slide or motorized awning, do they work? The slide is the real test of the battery, and if it works, the battery is good.
3) Are you connected to shore power, or are you on battery only? Again, if other things, especially the slide, are working, power is not the issue.
4) The thing that triggers the furnace is the thermostat. The furnace fan comes on first, and a sensor called a sail switch detects that the fan is running, and then the furnace will ignite. The fact that your fan doesn't start suggests that the thermostat is not calling for heat. Why? Less likely is a totally failed thermostat. More likely is that the thermostat is not connected to the furnace. I worked on mine to replace the sail switch. While in there, I just touched the thermostat wire connection to the furnace, and the wires fell apart at a crimp connection. Similarly, a wire may have come loose from the back of your thermostat...there are screw lugs to connect the wire to the thermostat.
5) Remove the thermostat from the wall and disconnect the wires from the back of the thermostat, you can SAFELY touch the ends of the wires together and see if the fan starts. (see videos) This "closes" the circuit as it would if the thermostat calls for heat. This is a low voltage circuit, so "shorting" the two thermostat wires together is a safe test to see if the thermostat has failed for some reason. You can buy a replacement from Amazon for about $25 that's much better than the factory thermostat: https://smile.amazon.com/Honeywell-P...862443&sr=8-13 Just use the heat side and leave the fan switch on auto. I put one in my camper because the last century technology installed by the factory was a POS.
6) So, if you have a good battery, and you have checked all the fuses, and you tried "shorting" the thermostat, and you've verified that the wire from the thermostat is still connected to the furnace, that last step means you've taken the cover off the furnace cabinet. Reach in and find the "on/off/reset" switch and "cycle" it (which means turn it off then back on). Now try the furnace. It may start after the reset. Resetting means you totally disconnect the furnace from 12 volt power, which MAY cause circuits on the control board to stop running then start again. Like any "reset," turn it off for about 30 seconds to allow any capacitors on the electronic control board to discharge and things to fully turn off. Then turn it on again.
7) Once you are in there, look for the main power wire to the furnace. This wire will go from the furnace cabinet to the back of your converter/fuse panel. Is it connected? FIRST, BE SURE YOU ARE NOT CONNECTED TO SHORE POWER...so you are only dealing with 12 volts. To be extra safe, you could also disconnect the battery...but that's not necessary. Then you can easily remove the whole converter and check the wires. Pull it out and let it rest on the floor. Maybe one of the lugs was loose and the wire came adrift. That would mean a lug is empty and the screw is loose...and a bare ended wire from the furnace cabinet is just laying around loose. You should be able to replace the wire and tighten down the lug....and check and snug up the rest while you're at it.
8) At this point, you can exhaust You-Tube help videos...and they are pretty good...if a bit boring. https://www.google.com/search?q=rv+f...hrome&ie=UTF-8 Here's another that's down the list a bit, but it looks promising: https://crowsurvival.com/rv-furnace-troubleshooting/
9) One option would be to throw some parts at it...a sail switch, a thermal overload switch...but, while I've replaced my sail switch, when I did it, the fan ran, but the furnace would not fire (meaning the sail switch was not functioning...which suggests a failed sail switch is not your problem, because my fan ran).
10) If you still have no luck, I'd turn to a pro to diagnose it. While others may have other suggestions, I'm at the end of my list. The videos may prove fruitful.
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Old 09-28-2021, 04:46 PM   #11
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Originally Posted by Larry-NC View Post
Bad advice.

To see the fan motor of a Suburban furnace you have to do some serious disassembly--only to find out there are no fuses inside. I don't think anyone puts an inline fuse on the furnace either.
Maybe bad for you. I never said the fuse would be inside. He didnít say what model it was. Some itís just a matter of removing the cover. It is sure way to find out where the comes from and stops.
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Old 09-28-2021, 05:00 PM   #12
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Lockout

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Furnace my be in lock out.
Is your fuse panel labeled?
Do you have a multimeter?
If furnace is in lock out you should turn it off and remove the fuse briefly to reset it.
Check fuses with multi meter by removing one at a time and testing with the meter.
Yes, lockout is a possibility. You don't have to remove the fuse to reset it. Just move the Cool-Off-Heat switch from Heat to Off, then back to Heat to cause a reset.
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Old 09-28-2021, 05:05 PM   #13
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Model?

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Maybe bad for you. I never said the fuse would be inside. He didnít say what model it was. Some itís just a matter of removing the cover. It is sure way to find out where the comes from and stops.
You think so?

There are a lot of water heaters and a lot of ranges and a lot of air conditioners, but I have never seen a post about any furnace other than a Suburban. And 99% of those Suburbans are the SF series. The others only differ in that they are designed for upright mounting, not flat mounting.

It's telling that there is ONE installation manual and ONE maintenance/troubleshooting manual for the entire line.
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Old 09-28-2021, 11:40 PM   #14
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Originally Posted by Larry-NC View Post
Yes, lockout is a possibility. You don't have to remove the fuse to reset it. Just move the Cool-Off-Heat switch from Heat to Off, then back to Heat to cause a reset.
I can't be sure, but I don't think the switch on the thermostat actually resets the entire power supply from the converter/fuse panel to the furnace. I think you'd have to pull the fuse or cycle the on/off/reset switch on the furnace cabinet.

My understanding is that the heat/off/AC settings merely choose which wire pair talks to the circuit board and switches on the furnace. If you were to remove the thermostat and short the heat circuit thermostat wires, the furnace would run. Opening this circuit merely tells the furnace to not run.
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Old 09-29-2021, 07:22 AM   #15
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Quote:
Originally Posted by jimmoore13 View Post
... Systematically pull each fuse and shine a flashlight through it from behind. Merely eyeballing the fuse can lead to a false determination. The light shining through from behind will reliably reveal if a fuse is intact or blown...big snip....

I have seen fuses that looked perfectly fine no matter how you looked at them but when checked with a multimeter they were open.
Most meters have an audible beep for checking continuity. Easy peezy!
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Old 09-29-2021, 08:47 AM   #16
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It does on both of ours

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I can't be sure, but I don't think the switch on the thermostat actually resets the entire power supply from the converter/fuse panel to the furnace. I think you'd have to pull the fuse or cycle the on/off/reset switch on the furnace cabinet.

My understanding is that the heat/off/AC settings merely choose which wire pair talks to the circuit board and switches on the furnace. If you were to remove the thermostat and short the heat circuit thermostat wires, the furnace would run. Opening this circuit merely tells the furnace to not run.
It certainly does on both of ours and both of ours are standard SF-series Suburban furnaces with reliable manual furnaces. While I was chasing a problem that turned out to be a failing propane regulator, I must have done this sequence dozens of times.

If I had been guessing, I would have said so.
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Old 09-30-2021, 10:39 AM   #17
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I have seen fuses that looked perfectly fine no matter how you looked at them but when checked with a multimeter they were open.
Most meters have an audible beep for checking continuity. Easy peezy!
Can't argue with that recommendation.
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Old 09-30-2021, 12:21 PM   #18
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Can't argue with that recommendation.
If possible the best way to test them is installed with power on and of course there should be full voltage on both sides. Testing with the beep sound is ok but some fuses will conduct enough for that very low current draw of the meter.
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Old 09-30-2021, 12:33 PM   #19
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You think so?

There are a lot of water heaters and a lot of ranges and a lot of air conditioners, but I have never seen a post about any furnace other than a Suburban. And 99% of those Suburbans are the SF series. The others only differ in that they are designed for upright mounting, not flat mounting.

It's telling that there is ONE installation manual and ONE maintenance/troubleshooting manual for the entire line.
Mine are Atwood, then Dometic, now Lippert. Take off the outside cover and the wiring is right there. I guess you consider that a lot of disassembly? Besides that cover should be removed periodically for cleaning anyway. I have seen a few as I have worked on them since the sixties.
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Old 09-30-2021, 12:48 PM   #20
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First suspect is always the thermostat. Pop the cover and sort the two wires to the furnace and it should fire up. Furnace is designed to not fire up until the fan states.

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