Gas burner shuts off but blower continues to run

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Old 03-09-15, 07:52 PM
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Gas burner shuts off but blower continues to run

I have a Goodman GMS950904 CXA gas furnace converted to burn propane (years ago). It was having problems establishing a flame and also staying running (flame would go out). I replaced one of the pressure switches and the inshot burner tubes and now it seems to fire up and run OK. But after the burner shuts off, when the thermostat stops calling for heat, the circulator fan continues to run. What is causing this?
 
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Old 03-09-15, 08:04 PM
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That Goodman furnace uses a timed method for blower on and off. You can also keep the fan running by putting the thermostat in the FAN ON mode. If the thermostat is in the the auto fan mode, try removing the wire that is on the G terminal on the furnace control board. See if the blower shuts off now.
 
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Old 03-10-15, 11:38 AM
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And the message is....

....never overlook sheer stupidity when searching for the cause of a problem!! The fan switch was indeed set to the FAN ON mode. I did the daylight savings time spring-ahead routine with the clock on that thermostat about two days ago. There's a small plastic slider that fits over the actual switch on the printed ciruit board. While resetting the clock that slider popped off the switch. In the process of pushing it back in place I apparently moved it from the AUTO to FAN ON mode.

Whenever two fails occur at or near the same time I usually assume they are related. This time, that was not the case. The other burner start/run problem was independent of the clock time change.

Thanks so much for the suggestion. I had just finished crawling through the wiring diagram and didn't see much to explain the always-running blower motor, except for the furnace control board itself.
 
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