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Coleman furnace model # 7956-856

Posted: Sun Feb 18, 2007 10:57 pm
by archive
Our furnace pilot is on, fan works, thermocouple was replaced at beginning of heating season this year but the furnace won't come on. The thermostat clicks but the furnace doesn't fire. The fan runs when the thermostat is switched to fan only. Any suggestions?

ckadee

Posted: Sun Feb 18, 2007 10:57 pm
by archive
Are you getting 24-28vac at the Gas Valve terminals ?

Did this just suddenly happen ? was it working fine up to this point ?

Thanks,
Robert

Posted: Sun Feb 18, 2007 10:58 pm
by archive
husbands checking on the vac but yes it did just happen suddenly. It was working fine yesterday and it happened sometime during the night.

ckadee

Posted: Sun Feb 18, 2007 10:58 pm
by archive
IF Pilot is remaining lit, Thermocouple is fine. Blower motor coming on verifies main voltage (120vac) and low voltage (24vac).

That also verifies the transformer.

IF your GV is getting 24-28vac, check burner orifice, burner tube for blockage (spider).

If all clear, need to have gas pressure checked.

IF GV is not getting 24vac, test across t-stat R and W, should read 0 vac with call for heat.

Take care and best wishes,
Robert