Furnace won't keep running

lostagain · March 27, 2018, 04:24:57 PM

All ducting is clear. So is the intake and exhaust. I looked at the sparker/flame sensor again. The ground rod was loose on the base plate. So, with nothing to loose, I tried welding it and burned right through... So went to town to the RV dealership to look for a replacement. They didn't have one, so it is ordered and won't be here till Thursday. Will go from there...

JC

Gary Hatt - Publisher BCM · March 27, 2018, 04:39:03 PM

JC, these appliances only last about 10 good years anyway. After that they get finicky. This not something you want to go bad while on the road so I think it is a good idea you decided to just replace it. Then you won't have to worry about it for another 10 years. You may even end up with a more efficient unit. After you get it, it should be about a 10 minutes job to pop the old one out and put the new one in and caulk around the outside.

If you bring it down to the Pahrump Rally, I will help you pop it in.

eagle19952 · March 27, 2018, 10:47:40 PM

is there a sail switch ?

oldmansax · March 28, 2018, 06:00:55 AM

My bet would be on the flame rod. When I was in the business, shutdown after a few minutes of operation was usually either a failing flame rod or a cracked heat exchanger. Here is how the rods work:

https://electronics.stackexchange.com/questions/148405/how-does-a-flame-sensor-or-thermocouple-operate-with-just-one-wire

TOM

lvmci · March 28, 2018, 06:34:33 AM

Hi JC, older units had a thermacoupler, with a pilot light, if it has one, that would also be an issue, easy replace and inexpensive, tom...

lostagain · March 28, 2018, 07:21:44 AM

Donald, the sail switch is good. I have tested it, as well as the limit switch.

Oldmansax, we will find out later this week when the new flame sensor arrives. I hope that it fixes it. Thanks for the link about how it works. The fire box/heat exchanger is good too. I looked at it.

LV Tom, it has electronic ignition with a sparking igniter controlled by a Dinosaur circuit board, which I believe is good, as it does what it is designed to do, with the little light doing its green and red thing.

If that new flame sensor doesn't fix it, I might drive the bus over a cliff... I don't know what else to do.

When driving home from down South last week, we had a propane catalytic heater overnight. The last night in Montana where it was colder, I ran the generator all night and had 2 electric heaters upstairs, and one light bulb in each baggage bay to keep the plumbing from freezing. When we get out of bed in the morning, I turn on the engine block heaters (2) for some time while we make coffee, etc. The geny is 6.5 kw. I wish it was bigger so I could run more electric things simultaneously. Like a 12kw would do. Or how about two 20kw generators like in some of the entertainer buses...

JC

TomC · March 28, 2018, 07:42:50 AM

Since it is pushing towards warmer whether now, if you can't figure it out, just get a new unit. As said before-they don't last forever. Good Luck, TomC

eagle19952 · March 28, 2018, 01:08:32 PM

Quote from: lostagain on March 28, 2018, 07:21:44 AM
Donald, the sail switch is good. I have tested it, as well as the limit switch.

JC

just tossing out clues

lostagain · March 31, 2018, 07:16:53 AM

New igniter/flame sensor didn't make a difference. Today I will hook up a 20lb cylinder for a supply to verify that the propane in the built in tank isn't contaminated. Although all other appliances work fine. I will re-check everything as per the troubleshooting chart. Let you know.

JC

luvrbus · March 31, 2018, 06:41:09 PM

The 100 dollar gas valve is bad

oltrunt · March 31, 2018, 06:48:15 PM

Sure could be luvrbus. I just replaced the 40 year old gas valve in my little bus-----and not a week later the same exact gas valve in the granny flat at my house!?! Jack

lostagain · April 01, 2018, 07:11:07 AM

Could be the gas valve. I have bench tested it by putting 12V to it. I can hear the solenoids click. I have taken it apart and it looks clean. Re-installed in the bus, the furnace will run forever with the end cover off, but shuts down after a couple of minutes with the cover on. So somethings gets hot and tells the board to shut down. And it is not the limit switch, because I have bypassed it to prove that. The gas just turns off and the light on the Dinausor board goes from red to green (red is gas on, green is gas off fan only). So I suppose a solenoid valve would let go when it gets too hot? Puzzled...

JC

chessie4905 · April 01, 2018, 10:54:52 AM

If the board is inside behind cover, move it out of there with jumpers, if necessary. Common for electronics to pull that crap with a component breakdown.

thomasinnv · April 01, 2018, 12:09:46 PM

Make sure that the exhaust and fresh air intake going thru the outside wall are in place and no cracks or pinholes, and no obstructions to airflow. Also make sure the combustion air blower wheel is free of debre, no broken/bent or missing fins.

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Dave5Cs · April 01, 2018, 02:19:54 PM

JC just info do you have and did you check the fuses in the thermostat and on the board in the unit?