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I have a 1987 Bryant Plus 90 model 398AAW NG furnace. Cold weather is here so I did my annual observation of the furnace to see that it starts and runs normally. Today it didn’t. Turned on the house thermostat to call for heat, induced draft blower starts, pilot lights, main burners fire up (normal sequence and delays) but the main blower motor does not turn on. After three minutes of the main burners firing they shut off along with the induced draft blower and at the same time the main blower starts up and runs for several minutes, then shuts off. After a short period of time the induced draft blower starts again and the sequence repeats itself. However, if I first turn the main blower motor on using the house thermostat’s “fan on” switch and then call for heat, the furnace cycles on and runs normally until the house thermostat reaches its set temperature and the burners and induced draft blower shut off. Everything functions normally as long as I keep the main blower motor running. Any ideas on what is the problem?
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Bryant Plus 90 398AAW Peculiar Behavior
The electronic board is not turning the blower on when it is suppose to, its waiting until the burner turns off on limit, and when that happens the blower comes on because of burner going off on limit.Originally posted by acwisn View Post
Turn the power switch off for 10 Min. and try it again. If it keeps doing the same thing. Change the board. Paul -
OK, thanks Paul. I ordered a board on line, looks like Bryant HH84AA021 replaces the original HH84AA015 board in my furnace. With shipping it is $89. It paid to shop around because I found a wide range of prices up to $223 for the same part number of board. I'll report back when I get it installed.Comment
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Installed the new control board last weekend. It was an easy swap out, two mounting screws and just moving wire spade connectors from old to new. The furnace has been working with no problems this whole week. Thanks again Paul.Comment
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