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Discussion Starter · #1 ·
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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The capacitor doesn't output 24 volts.

Hope you mean the transformer. If your not getting 120 volt to the transformer, its probably wired wrong.

How did you measure your 120 volts through the switch. Did you measure to ground, or to neutral.
 

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Are you sure you have the transformers line voltage wires on the right terminals of the board so it gets 120 volts? Did you check for 120 volts on those terminals.
 

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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.
 

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Discussion Starter · #8 ·
You guys were correct about the connections! I had the L1 wire connected to COOL and vice versa. Now I'm back to where the LED is solid and everything except the blower runs then shuts down with 33 this time.
 

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Discussion Starter · #11 ·
It says Limit Switch Lockout - Check for dirty air filter, check fro blocked return-air or supply grilles.
My filter is new and as far as I can tell there's nothing blocking the air intake, but I'll get a flexible wire and probe it again. What else can I check?
 

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Ohm out the limits. Your filter may have been too dirty for a while before you changed it, and the limit may now be stuck open. Also, could be that the capacitor for the blower is bad, and that is what caused the limit to trip, and why the blower doesn't run.
 

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Discussion Starter · #16 ·
There's a rollout switch on the burner compartment which is not tripped, but other than that there doesn't seem to be a limit switch for my model. I see one in the diagram for the 355MAV but not the 350MAV.
 

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Should be on the right side as I recall. Its not fastened to the burner compartment itself. but to the jacket. Your furnace has a high limit.
 

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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.
 

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Discussion Starter · #19 ·
Well guys I only found the rollover switch with 2 red wires and decided to disconnect them and turn the system on. Lo and behold the blower came on and ran. Feeling brave I reconnected the red wires to the rollout switch and again powered up the furnace. This time the blower came on and everything ran for about 2-3 mins before shutting down again with 33. Now at least I know that the blower is ok.
 

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You have a high limit somewhere.

If you have an open roll out. You may have more serious problems.
 
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