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spoke69 12-27-2012 09:02 PM

Blown carrier circuit board
I'm new & don't type well so please bear with me , My blower was not working had someone check that wasn't a tech but managed to hot wire motor to see if it worked , it did . so I called someone who service's hot water sys. & he thought it might be the circuit board but he doesn't know much about hvac . So he ordered new board , removed old & old board was burnt behind relay , changed bd. started furnace , still no blower . I switched the button on therm. to fan & the rest is history another $100 circuit bd for the trash . He is suppose to check with someone but I'm wondering if anyone has any thought's . I myself am a machinist & worked in engineering & am capable of using ohm meter's & I use to Drag race professianally & build motors but hvac is new to me . If anyone can point me in the right direction I would deeply appreciate it I can't afford another $100 bill out the window . Thank's

spoke69 12-28-2012 10:01 AM

The new cicuit board had a fuse , just wondering why it didn't blow instead of frying the board behind the relay .

Technow 12-28-2012 12:42 PM

The fuse is low voltage...not the 120 v to your board. What happened to the replacement board? I have a customer today that we hardwired the fan to run while I track down the proper board?

beenthere 12-28-2012 01:44 PM

Good chance the blower motor has a short in its windings. The short may be in the winding for the fan only/cooling speed, but not the speed that your friend used to test the motor.

As above, that is a low voltage fuse, not a line voltage fuse.

spoke69 12-28-2012 04:51 PM

First off thank you for the reply , I have both bds. (1) pn# st9103a1036 Honey well was the orig. from carrier , the repl. bd w/ fuse is pn# hqr99g004 from Acme , both have burnt relay . Thanks for the info on the fuse the Tech @ Acme didn't tell me that . I do know that my friend that is a licensed plumber not Hvac did jump the orig to run the blower , however I didn't pay att. to what wire it was because I don't like someone looking over my shoulder while I work so I did the same for him . besides that he was doing me a favor . I understand the short maybe in the fan "only" circuit but why didn't it come on when the furnace was up to temp ? that was why I switched therm. to Fan only & the fire works began with the new circuit bd ?

beenthere 12-28-2012 07:42 PM

Depends on how the motor is shorted. Might be almost a dead short on one speed tap, but not another.

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