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No LED on 350MAV Control Board

4960 Views 32 Replies 7 Participants Last post by  samworkss
I have a 350MAV036060F Bryant Plus 90 furnace whose blower had stopped working and control board LED was flashing 31.
I could cycle the emergency switch to reset but after a couple mins it would shutdown and flash 31 again. Having checked the meaning of code, I performed the following:
1. Checked the vents and intake PVC lines to ensure no blockage.
2. Checked the lines on the pressure switch.
3. Checked the condensate trap.
4. Checked the filter condition.

Not having solved the problem, I saw somewhere online I can test if the blower motor is good by jumping L1 and the blue 'heat' line. When I did that I heard a soft humming sound and the yellow LED went off. Fearing that I had messed up the control board (HK42FZ014), I bought one online and replaced it properly only to find that the LED is still off. I checked the 3A fuse on both old and new boards and it appears good. I used my multimeter and I am getting 120V coming thru the door switch when I tape it shut. I do not get any voltage going to the capacitor and thus no 24V coming out of it. HELP PLEASE!!
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L1 &PR1 are next to each other.Are your connections in the right place?Also is the replacment board the same as old one or is it the new updated conversion kit.Old style board was enclosed in black plastic , new is open .Code 31 ,remove trap and flush with lots of hot water and lots of shaking to get all the bugs out.More than likely if you have the older style press switch made of metal, this needs replacing because the vibration of ID motor makes the micro switch go bad internally.And yes even if you hear it click when you suck on the hose.I've found if you push the wire alittle sideways it works again, but replace it anyway.
33is open limit, so you may have a wire pulled off limit in blower compartment
I know 355 has limit on blower housing, but couldn't remember if 350 had it.Main limit is behind gas valve, ohm it out to see if it is open.Sometimes if it has tripped alot they dont reset, so take the handle of a long screwdriver and give the area next to the limit a good "wack", this usually resets it.
If the limit were open the fan would be blowing cold air.
Sounds like blower is ok , Do you have a wire on cool terminal and heat terminal going to fan motor?Cool usually black and heat blue but doesn't really matter the colors used.
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Common problem with old black CB is bad fan relay problem, which is why new replacment is different board.
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