Help me with my furnace problem PLEASE

macofpei · 09-03-2009, 10:14 AM

Voodoo Doll is at it again.
The furnace sometimes will fire and other times will not. It started this morning but the three mornings previous, only the fan cuts in and blows cold air. The thermostat works correctly. There is no apparent drop in voltage
I need the heat as we are leaving in a few weeks for our first rally and it will be chilly.
What do I need to check? I already replaced the regulator and hoses. The tanks are full. The water heater, stove/oven and fridge will and do run with the gas. No, I am not running them all at the same time so gas flow isn't at issue.
I am totally stumped.
1986 Excella 500, 32 foot, with the Original furnace.

Minno · 09-03-2009, 10:26 AM

Does the furnace generate a spark to ignite the gas after the blower comes on? Or it might be a glow coil. Sounds like no gas it making it to the burner, or the gas is not igniting all the time for whatever reason. Might be a bad circuit board in the furnace itself.

btw - you should be able to run all of the gas appliances at the same time without any flow issues.

Hope that helps.
Chris

macofpei · 09-03-2009, 10:42 AM

I honestly don't know what the inside of the furnace looks like. I do know that the gas is getting there because it ran the tanks empty on me before. It is not the easiest to get to, as it sits under the stove/oven.

astewart · 09-03-2009, 10:48 AM

Most issues I have had have been dirt (or a couple of spectacular wasp nests

) and having it blow itself out all the time. A good cleaning (and the recomendation is to remove, disassemble, clean and re-install) seemed to work. I didn't remove or disassemble mine (blew compressed air in the vent with a shop vac on the intake) but it works great now.

Good luck (and I had to use my furnace last Sunday on the north shore of Lake Erie!).

Alex

genearnold · 09-03-2009, 11:16 AM

I have two furnaces in my Limited and both decided to quit last fall. Thanks to a good friend who is a former RV tech they are now working (or at least they were working the last time I checked). The problem was dirty orifices in both units. Plugging both were tiny flakes of propane residue (at least that was my friend's diagnosis). It wasn't a complicated job if you knew how the furnace worked. I could probably tackle it myself if John wasn't available. Oh, yes, the fix involved very carefully cleaning out the orifices with a tiny copper wire and using compressed air to blow out as much debris as possible. He says the residue is a common thing in propane lines.

If I continue to have problems I think I will run a new line from the tanks just in case there is a bunch of stuff in the line.

Gene

jump · 09-03-2009, 12:19 PM

1. blower/fan generates air flow(my blower motor was not running and I had to replace the motor)
2. fly (micro) switch tells the control board that there is air flow and
3. control board tells the gas valve to open and
4. also tells the capacitor to fire in the chamber to ignite the gas
5. you have heat

if any of these steps fail you will not have heat...

If you decide to take the gadget apart, your local dealer should be able to test the control board and tell you if it is working properly.

The furnace has stickers all over it telling you to take it to a qualified technician for service...

IFyou feel qualified, look for a service manual before you attempt the repair yourself...and if you do, be certain to replace any and all gaskets when you take it apart...don't trust the old gaskets...clean the dust and soot out of the furnace...clean the burner element with a wire brush and run (gently) a hack saw blade across the slots (if it has slots...it might have holes, so use a wire, if so) to remove the soot from the burner element, then empty the soot from the element...don't even start if you don't have the mechanical ability...

macofpei · 09-03-2009, 12:59 PM

Thanks everyone who posted. I can see not firing if the orifice was plugged but that wouldn't explain why the furnace works sometimes and not other times. You would think that I wouldn't get heat at all if it was plugged or dirty. It is this hit and miss that has me stumped. Why today and not last evening or yesterday morning????

astewart · 09-03-2009, 01:15 PM

Mine also started as intermitant (seemed to depend on the wind, humidity and the moon phases

). Not that it is cleaner, it just works all night long.

alex

Minno · 09-03-2009, 01:32 PM

Some spiders like to build webs and nests in propane applicances. They can certainly cause intermittent issues as well. One thing to add to Jump's 5 steps: Even if the gas does not ignite, the fan will continue to blow until the thermostat is turned back down.

CrawfordGene · 09-03-2009, 01:55 PM

Mac,

Lots of things work intermittently before they fail. Dirt could lodge and dislodge, electronics are voodoo influenced. It is also very hard to get into the innards of our furnace which makes everything more difficult (the nature of RV's). My approach would be to do the simplest things first, clean whatever you can clean, and keep trying it. You may have to replace parts, maybe not.

I'll follow up about the dangers of propane. I have run gas lines, fixed appliances, and nothing has blown up (yet), but it always means being extracareful and I am motivated by fear to do it right. It's not rocket science, but you don't want to be the rocket. You probably knew this.

Seems early for Canadians to be chilly. I thought you had a few extra layers of skin or fur. We visited PEI in 2004 and it's bucolic. Charlottetown is just the right size for a capital city (or any city). Watching the legislature in action was fascinating.

Gene

macofpei · 09-09-2009, 01:23 PM

After "old Home week" out everning temps drop enought that we can get get early frost. I am going to try to clean the furnace this weekend abd I will look at the fly to be sure its bearing is working smoothly.I tried the heater this morning--- vodoo doll struck again.

alan · 09-09-2009, 07:19 PM

I had a similar problem with mine 2 yrs ago. I took it in twice for service (about $300) and the problem still occurred. The third time I told them to replace the furnace and no problems since.

Given the similar ages of our trailers, it might be time to replace the furnace.

Maryw164 · 09-09-2009, 09:32 PM

Ours did that until we realized that if the trailer was not level (side to side), or slightly leaning more to the curbside then it wouldn't blow hot. Terry (Overlander63) suggested that it probably was this and that it was preventing the switch that makes the circuit to allow the gas to kickon. Check on this maybe yours is the same problem. Now that it is always level it works great!

Good luck!

Mary

macofpei · 09-14-2009, 11:42 AM

Ok, so after receiving a note from Maryw164, I adjusted the balance of VooDoo Doll and low and behold-- the furnace worked !!!!!
I went to Walmart yesterday and bought a level assistant and will let you know if I have any other problems with the furnace. VooDoo Doll lost, this round.
Thank you Maryw164