Bad Thermostats

[Rick and Mindy]

Just a thought. Is the furnace getting enough gas to ignite? You might have a bad regulator.

[hoosierguy]

Originally Posted by Geo9350

I got the new motor, no change, still wouldn't light. I sent the control board back to Amazon and ordered another one. Put it in and it won't spark. I called the company Dinosaur and he had me ship it to him to see what is wrong with the control boards I am getting. So shipped it out today, will see what happens next. Kind of put a wrinkle in my plans, was gonna pull the RV up to Duck Creek Village Ut today, but that isn't happening. I wish there was a furnace I could buy to replace this piece of junk that has a pilot light. I hate these electronic starts, they fail too much. If anyone has replaced their furnace with one with a pilot light, please let me know.

Did you ever find resolution to your furnace issues? I am interested because I am currently in the process of removing my furnace so I can diagnose a non-operation issue.

[Geo9350]

This has been a real nightmare and cold nights for me. I replaced everything on the furnace including the gas valve, ignitor, fan blade, motor, over temp switch, circuit board and it still didn't work so I got tired of messing with it and took it in to a repair shop. Turned out only the motor was getting a good ground and the rest were intermediate so whenever I tested anything the ground was fine. I just picked it up from the repair shop yesterday so I will let you all know if it is working. Check your ground out real good if everything is fine.

[hoosierguy]

Originally Posted by hoosierguy

Did you ever find resolution to your furnace issues? I am interested because I am currently in the process of removing my furnace so I can diagnose a non-operation issue.

Well, it turned out that the issue that caused my furnace failure was a bad control board. It performed all of its functions except it would not operate the motor. When I tested the motor by itself, it checked out okay. Troubleshooting the furnace insert operation was the easy part of the whole process.

As Paul Harvey used to say, now for the rest of the story....................
My 2012 Redwood 36RL (built in Sept. 2011) has been used 3 to 5 months each year for past six years. The furnace has worked well and I have not previously had a need to even look at it.

My furnace is a Suburban model SVF-42. These furnaces have a blower and heat exchanger insert assembly that slides into a plenum cabinet. The plenum cabinet has a lot of perforations on one end through which the blower draws the return air. On the other half of the cabinet is where the five flexible ducts attach.

In doing some on-line research, I was able to download a service manual, installation manual and a troubleshooting guide. I also watched some YouTube videos. In the videos I observed that I should only have to remove the exterior rain cover, disconnect the LP gas supply line and disconnect the thermostat and 12 VDC supply leads and then one screw that secures the blower assembly to the plenum cabinet after which the furnace insert should slide out of the plenum cabinet so that it can be tested on the bench.

All went well up to the point of sliding the furnace insert out of the plenum cabinet. The insert would not move at all. Instead, the insert and cabinet seemed to be tied together. I finally decided to take down the storage compartment wall so I look at the furnace from inside the trailer. I found that the furnace was supported on an approximately 4 inch tall platform. There was one screw that fastened the furnace assembly with a bracket very loosely to the exterior trailer wall. I remove the screw and bracket. The five flexible ducts connect to the top and end of the plenum cabinet with a sheet metal bayonet type connection. There was not sufficient room to get the furnace assembly around all of the water lines connecting to the back side of the utility service bay. So, I decided to remove the rain cowling that the exterior rain cover attaches to on the outside of the coach. Once this was done, I was able to slide the entire furnace assembly through to the outside.

Once I had the furnace assembly on the bench, I was able to see why the heat exchanger/blower assembly would not slide out of the plenum cabinet. Suburban apparently ships the furnace to Redwood with 6 shipping screws in the cabinet in addition to the one screw that is supposed to remain for normal use. Apparently the day my furnace was being installed on the Redwood assembly line, the installer was “distracted” and forgot to remove the six extra shipping screws. As a result, there was no way that heat exchanger/blower assembly could ever be slid out in a normal manner in the event it needed to be serviced.

I have had to do some re-design and re-assembly of everything in manner that allows the furnace to be serviced in the manner that should have been intended. I am fortunate that all of this did not happen while I was out on the road somewhere. I would not have been happy with a several hundred dollars mobile service call. As it is, it has cost me about $114.00 for a new control board and sail switch. Also several hours of frustration trying to figure out why this wasn’t built in a correct manner in the first place.

Unfortunately, we were not able to go to Florida this winter. Also, fortunately we were not able to go to Florida this winter!! I was able to work on this issue in the comfort of my own barn/shop where I have tools and equipment to diagnose/repair this type of problem.

[Highcountrybarry]

Good work, I’ll record your lessons in the back of my mind. Maybe in my furnace manual for early onset days. Thanks for sharing and glad you now have it in order for future maintenance.


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[homeguy]

Our furnace went out yesterday during the day. We returned to North Carolina at the end of December. Came back from Oregon with a stop in Texas for a few weeks. Yesterday, my wife called me and said the furnace wasn't coming on. Strange because when I left in the morning, it was running. I get home and look and determined that it was not working. Insert I told you so here. She called a mobile repair service who said he could be there in a few minutes. He wasn't kidding as he just finished a job at another site in the same park. It also was our control board. We have used this camper daily since we bought it in 2012. He replaced the board and it started working. Then as he was putting everything back, he shorted something and no power to the thermostat. Luckily, it was him and not me. We have power at the main A/C-Heat pump, which is where it all begins, according to him. He installed a temp thermostat for the night and will be back today to trace out the issue. All fuses in the panel are good. Fuse in the thermostat is good, but no display. Stay tuned.

[hoosierguy]

Originally Posted by homeguy

Our furnace went out yesterday during the day. We returned to North Carolina at the end of December. Came back from Oregon with a stop in Texas for a few weeks. Yesterday, my wife called me and said the furnace wasn't coming on. Strange because when I left in the morning, it was running. I get home and look and determined that it was not working. Insert I told you so here. She called a mobile repair service who said he could be there in a few minutes. He wasn't kidding as he just finished a job at another site in the same park. It also was our control board. We have used this camper daily since we bought it in 2012. He replaced the board and it started working. Then as he was putting everything back, he shorted something and no power to the thermostat. Luckily, it was him and not me. We have power at the main A/C-Heat pump, which is where it all begins, according to him. He installed a temp thermostat for the night and will be back today to trace out the issue. All fuses in the panel are good. Fuse in the thermostat is good, but no display. Stay tuned.

Your furnace likely is same model as mine (Suburban SVF-42). I have two standard A/C's (no heat pumps). I found on my system the 12 VDC for the thermostat originates through the wiring supplying voltage to furnace. 12 VDC is supplied to the furnace where +12 connects to a furnace red lead and -12 connects to a furnace yellow lead.

The thermostat cable (similar to bell wire) has 3 leads as follows:
1. white wire connects to furnace -12 supply and furnace yellow lead
2. red wire connects to one furnace blue thermostat wire labeled as ++++++
3. green wire connects to a second furnace blue thermostat wire that is not labeled.

If any one of those thermostat cable wires is not connected properly, the thermostat likely won't function.

[homeguy]

You're right. Especially when 1 of them is broken like ours was. Wife just called and said he found a wire that was cut. Must have happened when he was replacing the board. Oops!

[GA1817]

Guy,

Just having similar problems and found your write-up while searching on-line. I am not to happy as mine was made in the same month and year as yours lol! Maybe a different person installed mine. Mine just quit as I can hear a click when I turn it on at the thermostat but the furnace fan does not come on. Was this similar to your problem?

[hoosierguy]

Originally Posted by GA1817

Guy,

Just having similar problems and found your write-up while searching on-line. I am not to happy as mine was made in the same month and year as yours lol! Maybe a different person installed mine. Mine just quit as I can hear a click when I turn it on at the thermostat but the furnace fan does not come on. Was this similar to your problem?

The click you are hearing occurs in the thermostat (a small relay) which sends a signal to the control board in the furnace. Normally the control board would then turn on the blower motor. After approximately 20 seconds, the ignition sequence starts.

In my case, the blower motor did start to run. Once I was able to get the furnace out of the coach, I was able to apply 12 VDC directly to the motor leads and found that the motor was operational, thus the control board was bad.

If you want to dig into it yourself, I recommend downloading the manual for your furnace model from the Suburban website. This will provide enough info to troubleshoot the issue. I chose to replace the control board with one from Dinosaur Electronics (FAN50PLUS Universal Igniter Board with Fan Control).

I was able to order all the parts I needed through Amazon.

Hope this helps.

[GA1817]

Thanks Guy!

[Geo9350]

I replaced my board with a dinosaur board also. The company that makes the board are very friendly and helpful. It turned out my board was fried and also after replacing it I was still having problems with it lighting. Talking to the Dinosaur Board company and helped me trouble shoot it, he told me I had a short because the voltage was dropping during the time the igniter is sparking to light the gas. I check the wire running around to the safety switch on the back side and sure enough on the underside of the wire next to the frame of the furnace it was blackened, burned and was shorting out to the body of the heater. Once I replace that wire and put an insulating sleeve around it the furnace lit off as it should and has been running great since. I had the furnace out so many times replacing parts and trying to figure out what was wrong I had the removal and installation down to a science lol. You have to remove the basement wall to get to it first and then screws are sometimes a real challenge to get to so you can pull the furnace out the side of the coach. It can be done, but plan on using some choice words, lol and anyway, I hope this helped someone. Dinosaur was a great help.

[GA1817]

Thanks Geo! The worst I ever say is "Gee My Nelly Knows". Learned it from my father who hated hearing curse words. I guess it rubbed off on me! I am reading a lot of good things on the dinosaur board!