Go Back   Thor Forums > Thor Tech Forums > Maintenance and Repair
Click Here to Login
Reply
 
Thread Tools Display Modes
 
Old 05-29-2019, 02:20 PM   #1
Junior Member
 
Brand: Thor Motor Coach
State: Idaho
Posts: 18
THOR #15465
Another Furnace problem

First post here Did a lot of searching and can't find a solution (I think), but have a few more questions. I just bought my 2016 ACE 30.2 from a used dealership that really specializes in boats, so their help has been minimal at best. Went on my first camping trip this past week and now onto my problem.

I started the furnace for the first time while camping this past weekend. Worked awesomely (is that a word), and then turned down the heat and went to bed. Woke up to a blaring fan in the bathroom that appears to be blowing air out. Never noticed a fan like this before. (came from a 2009 class C motorhome for four years) See pic below:


Tried the heat and nothing. Went to the back panel and hit the off/reset button. Fan came on in the furnace blowing air out of the the exhaust, but then would shut down after twenty seconds. The fan in the bathroom would remain on as well and will forever stay off till the heat is turned off. Looked at the LED light and I get the one light every three second message (No air flow/limit switch). Inspected the sail switch and appears spotless.

So what is next - limit switch then??? How often does a limit switch go bad? the heater worked once and heated great for about ten minutes till I turned it down and went to bed and have had nothing since then.

A few more interesting things: I plugged it into shore power right around that time I turned down the heat. Checked fuses and all intact at the panel under the bed. Is there another one I can check?

Also...all other appliances seem to be working great. Fridge, stove, etc. That use propane.

I don't think I can hear it try to ignite like I can when the fridge starts, so I don't think it is even sparking in there. Don't smell propane either.

Any ideas out there???
Attached Thumbnails
Click image for larger version

Name:	IMG_1139.jpg
Views:	81
Size:	212.6 KB
ID:	17726  
__________________

__________________
drzoomin is offline   Reply With Quote
Old 05-29-2019, 04:30 PM   #2
Senior Member
 
Brand: Thor Motor Coach
Model: 2013 ACE 30.1
State: Alberta
Posts: 908
THOR #2631
Hi, welcome to the forum and you have done “awsomely” so far. If you are not knowlegable around gas appliances you might want to have a mobie tech or RV dealer check this out for you to be safe. Or continue reading...



Just need to clarify something first.
The picture you show in the bathroom is a furnace heat output duct port......assuming my 2013 ACE is similar to yours. When you say the fan was blaring do you mean the fan is just blowing air strongly out the port or making a screeching noise like maybe the motor fan is dragging on metal parts of the furnace or the bearing on the furnace is squealing? The reason I ask is that if the fan is not turning properly it could result in failing to operate the sail switch during a call for heat from the thermostat OR if it passes that test, it may allow the furnace to start and then overheat since not enough air is being drawn through the combustion chamber/or from outside (around) the chamber for coach heated air. An overheated furnace should trip the limit switch which seems to be the LED code you are getting. I think that normally when things cool off the limit switch should reset automatically. Setting the code may have locked out operation though which is why you have to turn the thermostat on/off/on or operate the on/off switch in the furnace from outside. So the limit switch may just be doing its job (not actually failed)......but you need to determine if the fan motor/or squirrel cage fans on the motor shaft are functioning properly (just air noise); or the other issue could be a partially plugged combustion chamber (wasp nests etc) which is limiting air flow through the chamber. You do not want to overheat your furnace.


Now you say the furnace fan restarted when you called for heat.......but shut off again after about 30 seconds. This may be because the sail switch did not activate this time or the limit switch did not reset and is failed open now. The controller is shutting things down so you are not even getting to the gas valve opening or ignition cycle yet. You may also have a new code flashing now from this situation, which would require a furnace on/off switch cycle to clear it. If you have a voltmeter you should be able to carefully test for 12v coming through the sail switch and limit switch when the blower first starts up. Or you could use the ohm meter and test the limit switch for continuity (zero ohms cold) but turn off the 12v on/off switch on the furnace first or your ohm meter could smoke. You should have received a furnace manual that has the schematic inside.
__________________

__________________
javelin is offline   Reply With Quote
Old 05-29-2019, 05:48 PM   #3
Junior Member
 
Brand: Thor Motor Coach
State: Idaho
Posts: 18
THOR #15465
Man, I just typed a whole response, but somehow it got deleted, darn....

Blaring: It was just a loud fan. The door next to the bathroom was open and it is not far away from sleeping head when that happens. It was the first thing I heard when I woke up in the morning was that fan, so it 'felt' louder than it was. No screeching or metal on metal or anything like, just regular fan noise. I did misspeak above: The fan in the bathroom stays on if the heat on the thermostat is on. That fan in the bathroom does not turn off, only when I turn the thermostat to the off position (or cool position as well).

Just to clarify sequence of events: Turned on the heat for the first time. RV heated up in minutes. Plugged the RV into shore power, turned down the heat on the thermostat, and then went to bed. Woke to the fan noise in the bathroom. The furnace has produced no heat since that initial start.

I did visually check the sail switch. Looks intact and functional, no dirt on it whatsoever, like at all. It was spotless. I forgot about checking the switches with a voltmeter. I read about that and will do that later today and post if the switches are bad.

How does one check for limited airflow? When I turn on the heat initially, there is signifiant airflow coming out of the ducts. On the outside, I feel air coming out of the furnace vent. It "seems" as though airflow is not restricted.

Sadly, my Coach did not come with user manuals, so I cannot check anything like that with a manual...
__________________
drzoomin is offline   Reply With Quote
Old 05-29-2019, 07:15 PM   #4
Senior Member
 
Brand: Thor Motor Coach
Model: 2013 ACE 30.1
State: Alberta
Posts: 908
THOR #2631
Well that is good that the furnace blower motor sounds normal and you are getting good air flow. I guess for most of us, if the blower motor is able to close the sail switch when the thermostat calls for heat you jumped an important hurdle to getting a furnace to start OK. Next hurdle is the limit switch being closed (its in series with the sail switch, enabling 12vdc back to the control board if all is normal at that point). If the furnace then lights OK, but keeps tripping the limit switch, I would be checking the limit switch temp accuracy/operation and the combustion chamber for blockages. Gas appliance techs probably have the means for pressure testing the furnace fully I expect.


Your coach “should” have an equipment list posted in a cupboard somewhere (try the bedroom first) which lists the specifics (appliance/device; model #; serial # etc) of all the devices your coach is equipped with. You could check for the model info for the furnace (or any other major device)and then go on line to the manufacturer’s web site and down load your manual. Also there should be maker and model info in the furnace itself on the outside (cover off).
__________________
javelin is offline   Reply With Quote
Old 05-29-2019, 07:37 PM   #5
I Think We're Lost!
 
Bob Denman's Avatar
 
Brand: Still Looking
Model: Tiffin Wayfarer 24 BW
State: New York
Posts: 11,176
THOR #8860
By the way: welcome to the Forum!
__________________
Good Sam Member 843599689
FMCA Member F473304

Current coach: Tiffin Wayfarer 24 BW
Former coach: Thor Outlaw 29-H
Bob Denman is offline   Reply With Quote
Old 05-29-2019, 09:25 PM   #6
Member
 
Brand: Thor Motor Coach
Model: Thor Tuscany 40DX
State: Colorado
Posts: 79
THOR #5043
Just to check...did you run out of propane?
__________________
camperguy99 is offline   Reply With Quote
Old 05-29-2019, 09:57 PM   #7
Senior Member
 
The Gritz Carlton's Avatar
 
Brand: Thor Motor Coach
Model: THOR Chateua 35SF
State: Georgia
Posts: 3,658
THOR #11130
"Man, I just typed a whole response, but somehow it got deleted, darn...."

Every time you login, click the little "remember me" button just below the password. This will minimize getting kicked out. Also, on the real long wine responses..." right click n copy" your response just before hitting reply button...just in case you get booted...you can go back and "paste" it back in the text box. I learned the hard way too.
__________________
2018 THOR Chateau 35SF
Two Labs, Bugsie & Blondie
The Gritz Carlton is offline   Reply With Quote
Old 05-29-2019, 10:35 PM   #8
Junior Member
 
Brand: Thor Motor Coach
State: Idaho
Posts: 18
THOR #15465
Quote:
Originally Posted by camperguy99 View Post
Just to check...did you run out of propane?
3/4 full of propane. Burner inside lights up without issues and the fridge is running on propane.
__________________
drzoomin is offline   Reply With Quote
Old 05-30-2019, 01:56 PM   #9
Junior Member
 
Brand: Thor Motor Coach
State: Idaho
Posts: 18
THOR #15465
Checked the limit switch this morning. When tested there was significant resistance (which means it is ok, right?). There was resistance with the furnace off and on.

Just for curiosity sakes, I also tested the sail switch. When the furnace was off, significant resistance and when the furnace was on, no resistance (that is ok too, right?).

Guess I will have to take it in as I can think of anything else to do for it.
__________________
drzoomin is offline   Reply With Quote
Old 05-30-2019, 02:34 PM   #10
Senior Member
 
Brand: Thor Motor Coach
Model: 2013 ACE 30.1
State: Alberta
Posts: 908
THOR #2631
Hi, just heading out the door. The sail switch sounds good....when fan is not blowing it should have high resistance (open circuit actually) and the the limit switch should be a short (zero ohms) when cold. If it is open cct (high resistance) when cold it has a problem and will prevent the normal start sequence for the furnace.
__________________
javelin is offline   Reply With Quote
Old 05-30-2019, 03:29 PM   #11
Junior Member
 
Brand: Thor Motor Coach
State: Idaho
Posts: 18
THOR #15465
So maybe I misspoke (I hate voltmeters...I need to attend a voltmeter class sometime I think...).

When limit switch is tested with the voltmeter it is the same as when the two prongs on the voltmeter are touching.

Does that mean the limit switch is bad then? I thought i saw online, that is what is supposed to happen.



Maybe you are saying the same thing.

Thank for you help.
__________________
drzoomin is offline   Reply With Quote
Old 05-30-2019, 03:55 PM   #12
Senior Member
 
Brand: Thor Motor Coach
Model: 2013 ACE 30.1
State: Alberta
Posts: 908
THOR #2631
Back from the dog park.....
Well your video is for a house furnace but the limit switch safety function is basically the same as for an RV furnace. If the furnace overheats the limit switch opens its contacts (high resistance). The limit switch is normally zero ohms across its two terminals unless it has tripped open on over heat, or just failed open circuit (high resistance).


Using your ohm meter function on the multimeter is probably the easiest to do. Turn off your furnace so no 12vdc is on the circuits. Switch multimeter on to ohms and touch your meter probes together......you should see zero ohms on the meter. Some analog meters have a zeroing control that allows you to manually zero the reading; digital meters usually show zero right off or there may be a zeroing pushbutton. The main thing is with probe tips touching you should see zero or close to zero ohms. Then touch the probes onto the limit switch terminals.....or the appropriate wires coming from the limit switch if it is buried in the furnace. You should see the same zero or very low resistance value as when you tested the meter probes initially. If the limit switch is high resistance it will need replacement. You will need your furnace make and model number to buy a new limit switch. After replacing the limit switch monitor your furnace and if the new limit switch fails or trips open again then you will need to check air flow through the combustion chamber and also all output heat vents in the coach to make sure there are no blockages. I hope that helps.


By the way I "don't" recommend bypassing the limit switch with a patch cord other than to verify the furnace will start again. People typically leave the bypass jumper in place and then forget about it and wonder why their coach burned up. Limit switches can fail for no particular reason as well but you need to make sure its not from actual overheating.....without checking into it.
__________________
javelin is offline   Reply With Quote
Old 05-30-2019, 04:11 PM   #13
Junior Member
 
Brand: Thor Motor Coach
State: Idaho
Posts: 18
THOR #15465
Quote:
Originally Posted by javelin View Post
Using your ohm meter function on the multimeter is probably the easiest to do. Turn off your furnace so no 12vdc is on the circuits. Switch multimeter on to ohms and touch your meter probes together......you should see zero ohms on the meter. Some analog meters have a zeroing control that allows you to manually zero the reading; digital meters usually show zero right off or there may be a zeroing pushbutton. The main thing is with probe tips touching you should see zero or close to zero ohms. Then touch the probes onto the limit switch terminals.....or the appropriate wires coming from the limit switch if it is buried in the furnace. You should see the same zero or very low resistance value as when you tested the meter probes initially. If the limit switch is high resistance it will need replacement. You will need your furnace make and model number to buy a new limit switch. After replacing the limit switch monitor your furnace and if the new limit switch fails or trips open again then you will need to check air flow through the combustion chamber and also all output heat vents in the coach to make sure there are no blockages. I hope that helps.

Ok. So I did misspeak. It appears my limit switch is good then as the readings on the voltmeter are the same when probes touching and when placed on the leads on the switch.

Tested and visualized my sail switch. It appears good.

Anything else before I take it in? Does this have anything to do with the fan in the bathroom?

Thanks
__________________
drzoomin is offline   Reply With Quote
Old 05-30-2019, 04:34 PM   #14
Senior Member
 
Brand: Thor Motor Coach
Model: 2013 ACE 30.1
State: Alberta
Posts: 908
THOR #2631
Well if you are talking about the exhaust fan in the ceiling of the bathroom.....no there is no relationship other than both devices use 12vdc to operate. The picture in your original post is a furnace heat vent for the bathroom I believe. So that one should blow air when the furnace blower fan is running and heat when the furnace fires up.



Strange that the limit switch is now showing normal zero ohms (could be an intermittent problem with it. If both your sail and limit switches are normal then when you turn on the furnace power and set the thermostat to call for heat; propane on; your furnace should fire up OK. It is probably a good idea to have an RV service tech check this one out for you. Some mobile techs are very good if your Dealer is booked solid. When you find your problem please let the forum know as this helps others learn too.
__________________
javelin is offline   Reply With Quote
Old 05-31-2019, 02:16 AM   #15
Senior Member
 
Yvonnemarc's Avatar
 
Brand: Thor Motor Coach
Model: ACE 30.2
State: Massachusetts
Posts: 260
THOR #8180
The small fan near the floor in the bathroom is triggered by the heating system however, there is no duct going to it. It only draws warm air from the heat exhaust duct under where bunk duct blows heat out. If placed properly from the factory it should be directly across from that exhaust port and it will pull a small amount of heat into the bachroom. It works this way in my 2017 30.2
__________________
USN - RETIRED NUKE
Taunton, MA
Yvonnemarc is offline   Reply With Quote
Old 06-03-2019, 04:18 AM   #16
Junior Member
 
Brand: Thor Motor Coach
State: Idaho
Posts: 18
THOR #15465
Quote:
Originally Posted by Yvonnemarc View Post
The small fan near the floor in the bathroom is triggered by the heating system however, there is no duct going to it. It only draws warm air from the heat exhaust duct under where bunk duct blows heat out. If placed properly from the factory it should be directly across from that exhaust port and it will pull a small amount of heat into the bachroom. It works this way in my 2017 30.2
Thank you. That is exactly how it works. Didn't realize it was just a pass through.
__________________
drzoomin is offline   Reply With Quote
Old 06-03-2019, 04:25 AM   #17
Junior Member
 
Brand: Thor Motor Coach
State: Idaho
Posts: 18
THOR #15465
I solved my problem. Short answer it was the Sail Switch.

I called a local dealer and surprise surprise, they couldn't get it in for a few weeks. I thought to myself that this could not be that difficult of a problem to solve as it is giving me the error light!!! I decided that I was going to just wire the across either the sail switch or the limit switch and see if it fired up. I know, I know. Bad idea, but whatever, I wasn't going to leave it like that, and that way I could really identify if a switch was the problem. So off to work I went and didn't too far into my journey. I took out the sail switch and just depressed it and low and behold the furnace fired right now. Although a few moments later it cut out again, but it didn't cut out again after doing this procedure a few times. I put it back in place, screwed the switch back in and it was has worked since. The switch again appeared clean and spotless and appeared to be working fine the entire time. The switches are super cheap, so I will buy another one and put it in there. But it appears the limit switch is good and the sail switch is bad. I don't know how or why, but everything is workig correctly and thought I would/should post my followup so others can learn from my experience.

Thanks everyone for your. I have a few other problems that I will post in another thread.

Caleb
__________________
drzoomin is offline   Reply With Quote
Old 06-03-2019, 11:52 AM   #18
Senior Member
 
Brand: Thor Motor Coach
Model: 2013 ACE 30.1
State: Alberta
Posts: 908
THOR #2631
Glad you found your trouble. Thanks for letting the forum know what it was.
__________________
javelin is offline   Reply With Quote
Old 06-08-2019, 08:10 PM   #19
Junior Member
 
State: California
Posts: 21
THOR #10665
Sail switch can fail even if clean or no dust clogging it

I recently had to replace my sail switch on a 2018 Thor Freedom Elite Atwood furnace. Initially we thought we had solved the problem of the propane not firing up as there were a bunch of moderately thick strands several inches long of dust blocking the metal arm of the sail switch from fully closing with the air flow and depressing a small button (which is at the base/bottom of a V shaped design of the sail switch) which it’s designed to trigger or tells the propane there is proper air flow and allows it to flow & fire up. If it doesn’t work right it shuts down the fan and turns off completely within about 20 seconds. That little button the metal arm is designed to depress can fail as it’s usually mostly just a plastic part, although I’ve heard many do first try and slightly bent the metal arm to bow somewhat outward so that the air flow has more to push against and thus better depresses that little button or switch built into the sail switch. Now doing that may void your warranties so be careful what you say. However understand this, that sail switch usually costs under $7 and anyone can watch a 5 min You-Tube video and replace it in minutes. It’s very easy to replace as long as you can find the exact part. The paperwork I got with the purchase had the Atwood owners manual and ultimately identified the exact part number, so it can all be done without taking it in for servicing and minimal time/effort involved. However, if you feel uncertain or uncomfortable take it in and let the pros fix it, it’s a fairly simple & quick fix.
__________________
Kevad is offline   Reply With Quote
Old 06-09-2019, 01:32 AM   #20
Junior Member
 
Brand: Thor Motor Coach
Model: Majestic
State: Ontario
Posts: 1
THOR #14462
We had the same problem, woke up cold, but fan blowing. No heat. Checked and cleaned all wire connections and works fantastic now
__________________

__________________
RVGUY45 is offline   Reply With Quote
Reply

Tags
furnace, limit switch

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


» Featured Campgrounds

Reviews provided by

Disclaimer:

This website is not affiliated with or endorsed by Thor Industries or any of its affiliates. This is an independent, unofficial site.




All times are GMT. The time now is 08:47 PM.


Powered by vBulletin® Version 3.8.8
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Content Relevant URLs by vBSEO 3.6.0 PL2
×