| furnace backfire on ignition [message #242542] |
Thu, 06 March 2014 17:56  |
fred v
Messages: 999
Registered: April 2006
Location: pensacola, fl.
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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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