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Suburban Furnace Not Working

Furnace 2001 Casita

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#1 Charley in Tennessee

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Posted 27 August 2014 - 12:53 PM

I purchased a pretty much mint condition 2001 Spirit Deluxe about ten days ago and have discovered that I cannot get the gas furnace to work. I have plenty of propane and the stove burners work fine. A new double LP regulator was installed in April of 2012.  I have FINALLY discovered where the On-Off switch is inside the heater cabinet ( see photos ).( I hope these photos can be posted elsewhere, since I had a heck of a time finding it after reading several comments on how to find it.)Heater Box with Arrow.jpg Suburban Furnace On Off Switch with Finger.jpg Suburban Furnace On Off Switch.jpg The thermostat seems to be fine and the contacts close at the appropriate temp and are clean. The fuses and breakers are all fine as far as I can tell. When I reach in and turn the furnace switch to on, and call for heat through the thermostat, nothing happens at all. No fan blower comes on, no click or buzzing,...nothing. I have waited to see if my unit has a delay but still nothing happens. I am a real try to do it myself guy and know a lot about fixing things, but this has me stumped. My real weakness is electrical and how to check beyond OHM and voltage readings. The battery is new and has sufficient voltage. What are your suggestions ? As a newbie owner and forum member, I appreciate any help I can get.

 

 



#2 Wally Z

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Posted 27 August 2014 - 02:51 PM

I'm not real familiar with these furnaces, but in your picture it looks like you have one of those bimetal thermal protector switches.  It's in the first picture just below the big orange wire.  Try bypassing that by placing a jumper between the two wires, or just connecting the two wires together some how. (The two pink spade connectors)  Switches are wired in series so essentially that's one wire with a bimetal thermal switch spliced into it.  Won't hurt to temporarily jumper them together for testing purposes.  That is a safety device so don't leave it that way.  Sometimes exercising the bimetal disc will free up a stuck switch.  At least you'll know if it's the culprit.


Edited by Wally Z, 27 August 2014 - 02:53 PM.

2014 17' Casita SD


#3 Charley in Tennessee

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Posted 27 August 2014 - 04:21 PM

Wally, Tried the bypass on what they call a limit switch with no luck. BUT, you gave me an idea about bypassing the thermostat. I got to the wires where they run into the exterior case wall and they are connected to the two wires from the thermostat by blade connectors. Jumping across these two started the fan after a short delay, and I think that the rest of the cycle will work but I did not let it run the whole cycle yet. I have removed the thermostat and am trying to troubleshoot it now. Thanks for the tip and I will post the results when I get into the thermostat.



#4 Mark Watson

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Posted 27 August 2014 - 04:50 PM

My wall thermostat's contact looked clean, but my heater unit would not start the blower either. I removed
the cover from the wall thermostat,and with the lever set on say, 80 degrees, I tapped on the contact points with my finger and the furnace fan started up. I took a long strip of notebook paper and inserted it
between the open contact points (with the lever in the full off position), then closed the points by setting the lever to 80 degrees, and slid the paper strip back and forth, thus cleaning the points. This resolved
my hearter start problem.

Mark Watson

Houston,Tx
2008 17' FD


#5 Charley in Tennessee

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Posted 27 August 2014 - 06:11 PM

OK-Here is where things stand now. I removed the thermostat and took a close look and traced the conduction path from each of the wire contact screws. I then found out that this thermostat had a broken OFF switch and the lever was in the OFF position and this one contact was never to be made unless the lever was put back. Since it was broken off up behind the cover plate I never saw it since the tab should stick out below the cover. My best guess is that the most recent owner never boondocked and always used the strip heat in the ceiling. He might have never have known, and may have broken it off reaching for something above the sink, etc. I am the third owner of this Casita and am pretty sure he always used 110 since he uses a CPAP. He has ordered a new Casita with the newer twin beds conversion to allow him and his wife to get up seperately without climbing over each other. I have included photos of the broken lever and the "Optional" switch shown on the thermostat diagrams. However, now the fan turns right on after a very short delay and blows out the inside and the exhaust as well, but the flame never comes on. There is a long wait for the fan to shut off after turning the thermostat down, but I waited almost five minutes for the gas ignitor to fire up. No such luck. I then bypassed the limit switch and tried again with no luck. Is there another gas control valve on this unit besides the one at the LP bottles ? I certainly can't find one.  Maybe the photos can help someone who might have this really oddball problem with a broken OFF switch though. Suburban Thermostat Contact Closed.jpg Suburban Thermostat Contact Open.jpg Suburban Thermostat Diagram.jpg



#6 Wally Z

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Posted 28 August 2014 - 06:00 AM

It just may take longer than 5 minutes for gas to get going after never being used.  The fan should have a delay after shutting off the furnace.  That's normal.


2014 17' Casita SD


#7 Mark Watson

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Posted 28 August 2014 - 06:26 AM

Sounds like you found the reason why the blower never comes on. As for the gas not coming on and igniting, there is a "sail" switch that detects the blower is moving air through the heater. The air flow has to be strong enough to transfer the sail switch. For example

a very low battery condition could make the blower run at a slow enough speed to not transfer the sail switch. Once the sail switch activates, this closes it's contact points and completes the circuit to the gas solenoid. It sounds like your gas solenoid is not operating.  


Mark Watson

Houston,Tx
2008 17' FD


#8 Charley in Tennessee

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Posted 28 August 2014 - 01:36 PM

OK, I have moved the sail switch back and forth with a magnetic pick up tool. The force of the blower is such that if it gets much stronger, it will blow me out of the trailer, and the sail switch moves very freely....so maybe the contacts are dirty or something. I will try again tonight and let it run for a long time to see if Mark is right. If not, how would I fix the gas solenoid ? Take it to my local Camping World outlet ? I have one really close by. Thanks to all so far. It is reassuring to get so much feedback so quickly.



#9 Charley in Tennessee

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Posted 28 August 2014 - 03:57 PM

Ran the fan for fifteen minutes with no gas ignition. How hard is it to take out the furnace and how dangerous to work on this by myself ? Peace of mind might be worth the visit to the repair shop. I like to do things myself, but this is turning out to be a time is money kind of thing.



#10 Go Faster

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Posted 28 August 2014 - 04:07 PM

Hi Charley -

 

Have you gone through the troubleshooting guide and diagnostic steps in the service manual? Knock on wood I have not had problems with my furnace (yet), so I can't offer any useful suggestions.

http://brwholesale.c...vice_Manual.pdf


- Felix

 

2005 LD 17' (The TARDISta)


#11 Mark Watson

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Posted 28 August 2014 - 04:23 PM

Seems like the gas is ignited about 10 or so seconds after the blower motor starts. There was a thread post on this or the other forum about removing the furnace. I don't think it was difficult at all. Don't quote me seems like the front grill, couple of screws, a gas connection and an electrical connection and it slides right out. Perhaps the poster who removed his furnace will post info for you.


Mark Watson

Houston,Tx
2008 17' FD


#12 Charley in Tennessee

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Posted 10 September 2014 - 12:12 PM

Well.....I am a happy camper at this point. Thanks for all the replies. I found the problem and the furnace is working quite nicely. Now for the run down. Two screws are all that is needed to remove the front grill. Then there are supposed to be two screws holding the inner workings of the furnace, but whoever worked on mine last left them out after servicing it. I replaced them when re-installing it. Then two thermostat connections and two power connections need to be unclipped. Last, the gas connection is unscrewed and the copper pipe and end fitting is pushed back out of the galvanized mount box. The entire unit slides out very easily after tucking the wires still connected to the unit inside the case. After running an ohm check on the sail switch and tracing the wires I discovered a loose connector that had several connections that ran to the "motherboard". It had vibrated down and out of connection, or had been pulled out by me or someone else trying to find that darned on-off switch through the hole in the side. All I had to do was to re-connect the plastic fitting, clean the unit and check for obstructions in the furnace burn chambers and remove the ignitor and adjust the spark clearances. There are two. One for the ignitor hot and ground, and one for the spark above the actual burner gas holes. Re-installing all of this in reverse was simple, and turning the thermostat down was all it took. ( Must turn on that pesky on-off switch inside though ). Ran quietly and very efficiently. Here are the photos of what was the problem. Again, thanks for all the replies.

Attached Thumbnails

  • Suburban NT Furnace Tight Connection.jpg
  • Suburban NT Furnace Loose Connection.jpg


#13 Plainsman

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Posted 10 September 2014 - 01:15 PM

I've been fortunate and my furnace has been fine from the beginning. (Knock on wood!) But your photos and text are excellent and I shall file this one away "just in case." Thanks for the good work!


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#14 Euphoria

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Posted 12 September 2014 - 08:17 AM

Congratulations on solving your furnace problem. They can be a bit of a bear to troubleshoot sometimes. I noticed you still have the old mechanical thermostat. Have you considered upgrading to a newer digital t-stat? They are relatively cheap, (20~25 bucks for a Hunter t-stat,) and work so much better than the old mechanical ones.

 

I have one that I installed as a replacement for the old factory one which I use to control both my furnace and ac heat strips, using an added 12 vdc/120 vac 25 amp control relay mounted in the overhead cabinet near the 120 vac electrical box supplying the AC unit allowing me to control the 120 vac to power up either the heat strips (along with the propane furnace) or the Air Conditioning off the heating or cooling side of the t-stat respectively. The furnace and AC heat strips can also be independently controlled, so I can use one or the other or both, and I can also use the T-stat to regulate the Air Conditioner output to provide a more even temperature distribution than just using the one built into the AC unit itself which is "too close to the action" to be any good at setting the trailers climate for even cooling. I just leave the one on the AC unit set to "on" and "high", and control it from the t-stat.

 

Here's a couple of line diagrams on the installation, shown with and without the furnace, courtesy of Gene (webmaster) on the Casita Travel Trailer Forum:

post-1-1140657879_thumb.png  post-1-1140657894_thumb.png

 

He also has written up an excellent installation guide to this modification for those who may be interested. It is extremely detailed and has a lot of actual pictures of the installation process.

 

http://www.casitafor...tomatic-ac-mod/


Edited by Euphoria, 12 September 2014 - 08:57 AM.

"If I have seen a little further, it is by standing on the shoulders of giants."

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#15 jimrex

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Posted 01 December 2014 - 12:41 PM

I hope that I have success with the furnace on our 88 SD.  I have followed the steps in the manual and know that I have propane.  I can see the spark in the viewport but suspect that something is keeping the gas from reaching the spark gap.  The unit has a control valve as mentioned in the original manual, but I'm not sure which position in open or closed.


Edited by jimrex, 01 December 2014 - 12:44 PM.