| furnace backfire on ignition [message #242542] |
Thu, 06 March 2014 17:56  |
fred v
Messages: 999
Registered: April 2006
Location: pensacola, fl.
Karma: 0
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Senior Member |
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I have a Suburban furnace that has worked well for a number of years. Now it is hard to light off. It usually takes the 3rd attempt to light but backfires. Sometimes it stays lit and sometimes it blows itself out.
I have cleaned everything: burner, dirt dobbers in the combustion fan, plenum chambers. Gas is at 11" of water at the furnace. Voltage is at 12.5V. I have it on the bench to do this testing. The limit, fan and sail switches are all functioning correctly. The air valve on the back of the burner is almost fully open.
The flame is yellow when it first fires off or pops but quickly turns blue and burns nicely. It's when I open the thermostat and close it again that it doesn't want to light.
Any ideas?
Thanks,
Fred V
'77 Royale RB 455
P'cola, Fl
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| Re: [GMCnet] furnace backfire on ignition [message #242554 is a reply to message #242542] |
Thu, 06 March 2014 19:04  |
scott cowden
Messages: 170
Registered: February 2004
Karma: 0
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Senior Member |
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HI Fred;
I had that issue when I first bought my coach 12 yrs ago. In my case the furnace was like New Old Stock as it had never been lit in its 30 year life up to the point I bought the coach. All the paint was still on the heat exchanger, having never gotten hot enough to even scorch it.
It backfired quite noticeably a couple of times when I tried to light it and I realized that it couldn't be trusted to not do something dangerous.
I ended up removing the furnace [pretty easy to do, actually] and taking to a propane appliance repair place. the guy says to me, 'we don't fix stuff this old,' then, looking at the unit and seeing that it had never been used agreed to have a go.
He found an issue with the pressure regulator. I forget exactly [11 yrs ago now] what he found, but remember clearly he cleaned and adjusted the regulator and I was back in business. Cost me less than $75, I think.
A furnace that can't be trusted should not be used.
Hope this helps,
Scott
'74 x-Glacier
Newmarket ON [up here, we know our furnaces!! ]
> To: gmclist@temp.gmcnet.org
> From: fredntoni@cox.net
> Date: Thu, 6 Mar 2014 17:56:20 -0600
> Subject: [GMCnet] furnace backfire on ignition
>
>
>
> I have a Suburban furnace that has worked well for a number of years. Now it is hard to light off. It usually takes the 3rd attempt to light but backfires. Sometimes it stays lit and sometimes it blows itself out.
>
> I have cleaned everything: burner, dirt dobbers in the combustion fan, plenum chambers. Gas is at 11" of water at the furnace. Voltage is at 12.5V. I have it on the bench to do this testing. The limit, fan and sail switches are all functioning correctly. The air valve on the back of the burner is almost fully open.
>
> The flame is yellow when it first fires off or pops but quickly turns blue and burns nicely. It's when I open the thermostat and close it again that it doesn't want to light.
>
> Any ideas?
> Thanks,
>
> --
> Fred V
> '77 Royale RB 455
> P'cola, Fl
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