Furnace burner and blower won't turn off

Old 12-05-15, 03:41 PM
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Furnace burner and blower won't turn off

Carrier 58BMA105-12
Honeywell ST9103A1002 Electronic Fan Timer
Beckett Model "AFG" Series Oil Burner AFG DU201

The furnace had not been run since last winter but one night a few weeks ago the heat came on unexpectedly (thermostat in "off" position) and wouldn't turn off, I had to flip the breaker. Now the burner and blower come on immediately when power is applied regardless of thermostat setting. There are two wires (red & white) from the thermostat to the Honeywell board, I removed these at the board, there is now nothing connected to any of the G W R Y C terminals and the burner and blower still come on. I tapped on the relays on the board but there is no change. Is there anything else I should check or does the Honeywell board need replacement? If it is the board it looks pretty straightforward to replace but are there any settings or adjustments to be made besides the blower delay off timer dip switch?

Thank you!
Old 12-05-15, 05:02 PM
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Welcome to the forums.

I concur with your diagnosis..... the control board needs to be replaced. Depending on if the board is a substitution.... there may be some minor things to be set. Blower time is one thing. Shouldn't be anything major.

Here's the manual to your oil fired furnace.
hvac partners/docs/1009/Public/0E/58BMA-4SI.pdf

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