[stick_boy1106]

I have a Carrier 58mca furnace with a HK42FZ016 control board. It flashes code 24 when no call for heat is active then flashes code 21 once a call for heat is initiated. The inducer motor and blower start up but the ignitor never glows to ignite burners. I have checked the 24 vac is properly supplied from the transformer. I attempted to run a component self test but it will not run. If I keep the test/twin shorted to common it does flash the LED rapidly recognizing the attempt. Thoughts on where to proceed to next?

Thanks!

-Wes

[yuri]

code 24 is secondary fuse blown. should be a 3 or 5 amp plastic gm auto fuse on the circuit board. if it blows again then you have a short in the wiring.

[stick_boy1106]

I checked the fuse and it is not blown. I also disconnected all the thermostat wiring from the control board and the code 24 remained.

Cheers,

-Wes

[yuri]

Probably a bad circuit board as it is giving false readings. Should not give the 2nd code as it cannot initiate a call for heat with a blown fuse. Try americanhvacparts.com for carrier parts

make sure you have a proper 120 volts to the furnace. 120 from hot to ground not neutral, 0 from neutral to ground and continuity from the green ground wire to a copper water line. use a cheater wire from water line to your meter if necessary. if you have reversed polarity or a bad ground or neutral it can give false readings. rare but possible.

[fy171]

try ebay i bought newboard replacement for $99