Blown carrier circuit board

1474 Views 5 Replies 3 Participants Last post by beenthere, Dec 29, 2012

spoke69

Discussion Starter · Dec 28, 2012

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

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spoke69

Discussion Starter · #2 · Dec 28, 2012

fuse

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

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Technow

· #3 · Dec 28, 2012

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?

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beenthere

· #4 · Dec 28, 2012

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.

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spoke69

Discussion Starter · #5 · Dec 28, 2012 (Edited)

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 ?

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beenthere

· #6 · Dec 29, 2012

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

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