Furnace won't light

bennydog · 04-12-2010, 04:14 PM

Well I was hoping that she would awake from her long winters nap with no issues and we almost made it. Last item on the check list was the furnace and she no light. The fan comes on and after a purge time if I stick my ear on the air intake I can hear the igniter rapid fire wait 15 seconds and fire again and then again. Fan continues to run for awhile to purge and then shuts off. I have to reset the thermostat to get it to try again, which I expect. When I'm outside with my ear to the intake I never smell any gas, none not even the slightest hint. 1st question is should I? Could this the a spider caused issue and if so how in the world would you remedy? This thing is stuffed in under the fridge and the gas and all the wiring are on the far side. You would have to stand on your head with a mirror to even begin to be able to unhook to remove.

I tried blowing air using my shop vac / blower into both the air in and exhaust with no change. Any thoughts would be helpful.

BTW we did get a mouse in the trailer, first one in 4 years and I'm really going to need to look hard to figure out how it got in as we have a sealed underbelly. The reason I bring this up is I hoping that it's not wiring. given the facts that the fan comes on and the ingniter fires. At least not wiring to the unit.

I replaced the thermostat last year with a setback type from the house and the furnace seemed to work fine. If I take it in for warranty I can just here them now. I tossed the old one.

Flyguy · 04-12-2010, 05:59 PM

Well I don't know how your furnace works but with mine I have to light a burner on the stove to purge all the air in the line so that I know that gas is getting there and it takes quite a while before it does, when the top burner on the stove lights then and only then will I try to light the furnace, if I never get the stove to light I start looking at the gas supply bottles. All of this is when the trailer has been sitting for days with the gas supply shut off.

bennydog · 04-12-2010, 08:19 PM

So the stove and the fridge are all at the back of the trailer and I changed LP bottles then lit all 3 burners on the stove and made the fridge run on gas both of which worked as expected. The furnace has should have gas.It's like the solenoid is not opening the gas supply or it's somehow plugged.

Jim W · 04-13-2010, 03:45 AM

Is there not a thermal coupler that needs to function in order for the furnace to ignite? This is the first area to look at since you are sure you are getting gas there. I would check out the thermal coupler to see if it has failed. Just an idea I have for you to look at.
Jim

Flyguy · 04-13-2010, 05:02 AM

If you have gas at the valve and the ignitor operates, then check for 12v at the valve on the plug in lead! If that's ok then clean the burner orfice (assuming that the valve is opening).

bennydog · 04-13-2010, 04:12 PM

Thanks for all the suggestions. I'm attaching a couple of pictures just to show what a challenge it's going to be to try and work on this thing. There's got to be a way to figure it out without taking it out.

bennydog · 04-20-2010, 04:23 PM

I've about given up on trying to bring this thing back to life on my own but want opinions on one last thought. So just to recap, when I set the furnace to on I hear the rapid fire of the igniter and a clunk of what I think it the gas valve solenoid. This repeats 2 more times and then the unit purges and shuts off. If I turn it off and back on it will do it all again. I have tried using my shop vac blower blowing into both the exhaust and the intake holes on the outside of the trailer to see if I can shake the cobwebs loose with no luck. LP gas is delivered after the regulator at about 7 psi I think. If not 7 it's not a very high pressure. Does anyone think that (after turning off the gas) if I disconnect the furnace gas line and using compressed air at say 30psi that If I cycle the unit that IF it is cobwebs that I might blow them out without damaging the furnace? I'm really trying to avoid taking the damn thing out to get for spiders and I don't want to drive it 100 miles to the dealer to have them tell me it's spiders as I'm sure that is not a covered warranty item.

Thanks

Bob

Flyguy · 04-20-2010, 08:19 PM

Everything that you say about the operation sequence is normal and the only thing missing is gas. The proper LP pressure is 11" on the water column which equates to 0.48psi if I remember correctly, if you measured 7psi that's way too much pressure, might want to check the regulator and reset it if it's off. I don't think I would put 30psi of pressure on the gas valve; instead you need to check the gas pressure that's there at the valve and make sure it's normal as stated above.

Jim W · 04-21-2010, 03:57 AM

Have you measured the voltage to the gas valve yet? Is the voltage within tolerance for the valve to open? Or have you checked the limit switches, to see if they are functioning correctly? I had a limit switch go bad once and the gas valve would not open. Just another thought.

bennydog · 05-28-2010, 03:23 PM

I ended up taking the trailer back to dealer to have this worked on. Turned out to be a defective gas valve which Keystone covered under warranty. I had to giggle when I saw the itemized bill....dealer asked for and got authorization for "additional time". Too bad when the designed the hole they put the furnace in they didn't think about how serviceable it would or would not be. Happy ending and we're going camping this weekend.

Safe travels to all.

Bob

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