Duo-Therm Furnace Shutting Off

87Itasca · October 18, 2016, 11:55 AM

Hi all,

I have two Duo-Therm furnaces in my Windcruiser, Model # 90130.002. One is inoperative (powers on, but doesn't ignite), and the other one has an odd issue.

I turn it on, the blower kicks on, it ignites. Runs fine, gets up to temp, cuts in and out as the thermostat dictates. Then randomly, all of a sudden while it's running, it shuts off. Then the lights inside the unit will dim as it tries to kick on. Sometimes it will, sometimes it gets halfway up to speed before it cuts out, sometimes it doesn't turn at all. Accompanied by the dimming is the sound a blower motor makes as it is turning on.

If I shut off the thermostat when it's having an episode, it will still try to kick on for a minute or two, then it stops. If I let it rest and turn it back on, sometimes it starts and runs fine, sometimes not. A "popping popcorn" kind of sound can sometimes be heard, this goes on in sync with the dimming of the lights.

There are no blockages in the intake/exhaust ducts. I have taken them out all the way to the blower motor and inspected them. It doesn't seem like the blower motor is actually bad, rather, something that sends the signal to the blower motor to run. The blower makes no odd noises that would lead me to believe a bearing is going bad, and when it is operating, there is plenty of airflow out of the ducts.

I'm hoping I can piece together one good unit out of both of these.

Rickf1985 · October 18, 2016, 01:17 PM

I would say either the motor shaft is seizing up or you have a wire shorting out somewhere. If it is the wire you better find it before you continue or you could have a fire.

87Itasca · October 19, 2016, 01:37 PM

I spun the blower by hand when I had it apart getting to the ductwork, it spins freely, without a lot of resistance, so I don't think that is the problem.

I've gone through all the wiring I see (minus the thermostat wiring) and everything is in it's place, all the connectors are a snug fit.

I'm wondering if it would be easier to troubleshoot the other one, as it has no problems, aside from it not igniting. It will "click', but it will not light. It's getting gas to the furnace.

I only need one really, the rear one does a good job of keeping it warm on even the coldest days. I'd imagine two would be overkill.

legomybago · October 19, 2016, 02:32 PM

QuoteI'm wondering if it would be easier to troubleshoot the other one, as it has no problems, aside from it not igniting. It will "click', but it will not light. It's getting gas to the furnace.

Does it just "click" once? Or does it click, click, click doing it's firing cycle?

Rickf1985 · October 19, 2016, 05:42 PM

Quote from: 87Itasca on October 19, 2016, 01:37 PM
I spun the blower by hand when I had it apart getting to the ductwork, it spins freely, without a lot of resistance, so I don't think that is the problem.

I've gone through all the wiring I see (minus the thermostat wiring) and everything is in it's place, all the connectors are a snug fit.

I'm wondering if it would be easier to troubleshoot the other one, as it has no problems, aside from it not igniting. It will "click', but it will not light. It's getting gas to the furnace.

I only need one really, the rear one does a good job of keeping it warm on even the coldest days. I'd imagine two would be overkill.

It may spin with no load but when powered up if the bearing is bad the armature may be shorting out on the windings. The magnets will pull them together. Just an idea.

87Itasca · October 19, 2016, 10:23 PM

It clicks three times, then goes into lockout.

I could try swapping the blower motors and see...swapping the igniters or something might be easier though.

legomybago · October 20, 2016, 09:47 AM

swap the computer boards

CapnDirk · October 20, 2016, 08:00 PM

Has the motorhome been sitting for a while?

yellowrecve · October 20, 2016, 10:18 PM

Take the motor and connect it to a 12v source (battery) and see what it does.

87Itasca · October 21, 2016, 08:24 AM

The RV had sat for (According to the tag) 10 years when I got it. Don't know if it was used any after it was taken off the road or not.

I cleaned out all the wasp/dirt dauber nests in the vents when I got it, as well as opened the units up to check for any inside (no nests).

I'll try to do some troubleshooting/swapping either this weekend, or this coming week.

tmsnyder · October 21, 2016, 09:36 AM

Mine sat 10 years or more too, working on it last night, the heat exchanger was completely full of wasp nests and mud dauber nests. I ended up running the garden hose through it for 20 minutes, shaking the bejeezus out of it, running water, repeat until nothing else seemed to be moving around inside when I shake it. It was amazing the amount of stuff that came out of the furnace.

Ideally I would have liked to dumped in some gravel or a bunch of nuts and turned it on a lathe for a day or so to try to clean up the inside really well, but it should be ok I think.

Mine has a center section in the heat exchanger that can not be inspected visually, and it was right full of nests.

Just put in a new motor also b/c the old one had a bearing that was totally shot. Would blow the fuse immediately.

CapnDirk · October 21, 2016, 03:18 PM

The reason I ask about sitting is what happened with my propane water heater. I got all propane stuff working, but then had trouble with it cutting out, sputtering and popping. Couldn't figure out why when everything else propane was working fine. Then I remembered that when I had removed the regulator from the propane tank and let it dangle I was surprised to have what looked like motor oil come out of it. I replaced the regulator and hose, and the other stuff was fine. I theorized that maybe there was a low spot in the copper line going to the water heater, opened the joint underneath the motor home between the pipe and soft copper and put my compressor nozzle to it. Blew 1/3 cup of oil onto the ground. Blow out the lines only when disconnected from appliances and regulators. or you're going to blow the junk into something important.

The oil was too heavy to push through the line by 1/2 psi of propane. After that the heater was fine. Apparently propane goes heavy if sitting for a while. I'm in the process of removing the tank to flush it out.

Rickf1985 · October 21, 2016, 05:53 PM

Interesting, a friend of mine hauled propane for many years as a trucker, I will ask if he has ever heard of that. I had also noticed the oily gunk in the old regulator I changed out a few years ago on mine.

yellowrecve · October 21, 2016, 10:41 PM

It is true. Propane that sits in regulars and lines for a long time unused, can cause an oily sludge that will not pass through the jets and will plug lines in low places. "DO NOT TRY BLOWING THE OIL THROUGH THE JETS." Disconnect the lines from the appliances and regulator.

CapnDirk · October 22, 2016, 12:02 AM

Thanks for the catch Yellow, I had mine disconnected, but someone may not assume to do so. I've edited my post.

87Itasca · November 08, 2016, 10:00 AM

I'm going to pull it out in the next week or two and see what I can see. It's not easy to get to, unfortunately.

I think I have two problems with it, the first being the issue with it shutting off, and the other being an intermittent problem igniting.

When it does ignite, it will run fine and stay lit until it starts to cut out. It's like someone flips a light switch and kills the blower. Once this happens, and it sorts itself out and starts to run long enough for the board to call for the propane to ignite, the blower will either cut out as soon as it lights, or it will not ignite. Sometimes it does, and works again for a bit, but it's not reliable.

Sometimes I have to cycle the ignitor 20-30 times for it to ignite, sometimes I just shut it off for an hour and try again.

Honestly tempted to just replace it with another one. Is there a drop in replacement for the Duo-Therm 90130 series? Don't want to cut a hole in the side of my RV for a new furnace if I can help it.