repairing Uhaul furnace

[Bridget T]

Ok, so now I will post some photos and discussion of my ongoing Uhaul furnace repair.
First the thank yous: Thanks to Karen W for sending me her old furnace for shipping only, and to Roy in TO for convincing me to come to the Niagara NOG, and to Mike S who at Niagara actually showed me how to pull out the furnace and advised me what to work on next (sorry I didn't bring the spare furnace to Niagara Mike, I honestly didn't imagine that anyone would really want to help me try to fix it!)

The Uhaul furnace is a Duotherm something or other. It is self igniting. Mine would ignite - light up for about 5 seconds and then die. I tried burning the stove to get rid of oxygen in the line - still the same. We tried a bunch of other things, still the same, read the manual.... got confused.
Once Mike and I pulled the furnace apart and looked at what was happening he felt that the board was likely the problem... so here is what I did to replace it.

First you need to get to the furnace. On the inside of the camper you need to pull off the trimlock surrounding the cutout and open up the access panel next to the furnace (mine just has a piece of plain fiberglass covering a hole on the side of the furnace). Then you pull the brown cover off the furnace. If you look at the picture of the back of it you might see the two clips on either side of the grate that clip onto the front furnace edge. On mine I actually had to slightly loosen the outside screws holding the vent cover so I could push the furnace back a bit, then pull off the cover and wiggle it out.

[Bridget T]

Next step is to get the furnace out.
First step - undo the screw holding it in at the bottom. Then undo the propane gas line (make sure outside propane is off).
Now you can pull the furnace out partway.

[Bridget T]

The reason you only take it out partway is that you need to undo the electrical.
Here is a shot of the electrical - take a photo or mark what goes where for putting it back together. Make sure the + and - don't cross or you will blow a fuse (unless you have sensibly unplugged the electrical prior to this work - which of course we all do).
Once undone - pull the furnace straight out to get it free!

[Bridget T]

The next step is to reveal and release the furnace board. Two screws hold the metal cover on. Once this is loose you can see the board. To release it you need to remove 4 screws and unhook it from electrical at 2 points.
You can also see in one photo the other board I got from Karen W's furnace.

[Bridget T]

So, now you mount the new board. I had to drill new holes as it was a little smaller than the old one.
To replace the furnace, rehook electrical (properly based on photo or labels), rehook the propane, slide furnace back into place and then try it!

[Bridget T]

So, for me, as soon as I reattached my electrical my furnace fan started going. (Yes I admit, I did this work without unhooking from the electrical system - Mike, I cite you as a bad influence!).
And then once I turned on the propane my furnace lit up and stayed on - Yay!
Except it kept going and going and going, no matter what I did with the thermostat. And so did the furnace fan - just kept going and going.
So I have turned off the propane, and disconnected the electrical. My next plan is to buy a new thermostat. Then we shall see how she works.
Still - pretty excited to get the furnace working. Apparently the board is a dinosaur board which can cost 100$ on the internet, but thank you Karen W for giving me your old one.
To be continued....
Bridget

[Raya]

Ahh, the blue flame of success

(Oops, just read your next post about needing a thermostat, but still, it works!)

[KarenW]

I am thrilled my old heater was helpful. Be sure and post a photo once you finish the repair and are all cozy in the camper with the heater going!

BTW: thanks for the curtain wire... I was 6 inches short with what I ordered, so yours was a life saver...

[Bridget T]

Yes, I am pretty stoked! Once Mike showed me how to pull the furnace out I felt quite comfortable doing it myself. It is always good to know when you can and should just give'r and when to be more careful.
And despite my frustration with trying to figure out the problem while it would not turn off, I must say it got very toasty in the camper.
Any advice on thermostats everyone?

[Bridget T]

Karen,
Yes, thanks for the furnace - even though I seem to have only needed 1 little part! Anyone who wants the rest of the furnace, contact me - I suspect it will work with a new dinosaur board. (I will post in pay it forward once all is done).

Glad you could use the curtain wire, you deserved it for lugging and packing up the heavy furnace for me!

Bridget

[nick c]

would not turn off, I must say it got very toasty in the camper.
Any advice on thermostats everyone?[/QUOTE]

I would remove wires R and W from t-stat, jumper them together simulates call for heat from t-stat, and light furnace. Once lit and running remove jumper thus breaking circuit. Is furnace goes out stat problem, it continues firing, problem with wire back to furnace or way wires were re-attached.

[Matt in SV]

When you do get it working, you might consider spraying the heaterbox with some flat black high-heat paint (rustoleum BBQ variety). Put a piece of tape over the spyglass and any electrical connections. And let it run for four hours or so to outgas any paint fumes. It will slow down the rust and make it look more serviceable.

Regards,

Matt

[Bruce Thomas]

Matt (or anyone)...when I picked up my uhaul last year the furnace wouldnt light and then it did after a few days.i thought it had something to do with my charging the battery but I guess not.....now mine cycles through like its gonna light but doesnt.......any idea's? and can I take it out and bring it to a heating and ac joint or will they be lost?......thanks bruce

[Matt in SV]

Mine is different in the VT they used one of the fan less "gravity variety" so it doesn't take any power, Bruce. But for yours, there is a troubleshooting page in the trailer repair guide in the Document Center in the Manufacturers section under U-haul that covers the direct spark ignition model heater. In my hardcopy it starts on page 26.

Is the fan kicking on?

[Bridget T]

Bruce,
From my minimal knowledge of our furnaces I wonder if it is the dinosaur board. This is the thing I show myself changing in the pictures in this post. My furnace did the same thing - would light for a few seconds and then the flame would die out. It seems like the board controls the continuation of the flame, among other things. Someone knowlegable on this, please pipe in.
While I just took the board out of Karen's furnace (and the verdict is still out as to whether it is working for me - it could be the board and not the thermostat that is malfunctioning and keeping it on all the time - will try to work on it during this long weekend - the real Thanksgiving ) you can also buy a new board. They are called dinosaur boards, and I might be ordering one, we'll see.

Ignitor Board Index page

Originally Posted by Bruce Thomas

Matt (or anyone)...when I picked up my uhaul last year the furnace wouldnt light and then it did after a few days.i thought it had something to do with my charging the battery but I guess not.....now mine cycles through like its gonna light but doesnt.......any idea's? and can I take it out and bring it to a heating and ac joint or will they be lost?......thanks bruce

[Bruce Thomas]

Matt....yes the fan runs and the thermostat works...Bridgett.thanks for the link..I guess i better get diagnosing and get whats needed..it was cold here in that thing friday!.......Bruce

[nick c]

Originally Posted by Bruce Thomas

Matt (or anyone)...when I picked up my uhaul last year the furnace wouldnt light and then it did after a few days.i thought it had something to do with my charging the battery but I guess not.....now mine cycles through like its gonna light but doesnt.......any idea's? and can I take it out and bring it to a heating and ac joint or will they be lost?......thanks bruce

sounds like the board does not recognize the flame has lit. Solution for this is to clean the flame rod with 000 steel wool and make sure it is situated in the flame. The flame retification system requires good grounds so you also want to check the connection to the rod, the wire, and the connection to the board to ensure they are clean, snug and sound.

It's critical that polarity of power source is correct.

[Bruce Thomas]

there's no flame to recognize...it doesnt light ....at times i see the sparking where its trying to light something and thats it now...Bruce

[nick c]

Originally Posted by Bruce Thomas

there's no flame to recognize...it doesnt light ....at times i see the sparking where its trying to light something and thats it now...Bruce

when I picked up my uhaul last year the furnace wouldnt light and then it did after a few days.

As you are able to view sparking and no flame, and as it did work last year after trying multiple times, I would purge the gas line to the furnace. You can follow the line back to the next appliance nearest the furnace, light that appliance and fire for a minute, then cycle the furnace a few times till it lights. OR loosen the gas line at the gas valve and purge gas to atmosphere. (Only talking a little ...10 sec.) Ventilate well, no nearby sources of ignition. (against gas code, considered not safe practice with out use of approved purge burner) (propane heavier than air will want to fall out open door.)

If your hearing is good, you should be able to hear gas flowing/hissing out at burner as you view the sparking. If not flowing, burner oriface may be obstructed and require cleaning. ie: spider webbing. Hope that helps...