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Old 11-23-2012, 11:58 PM   #1
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No LED on 350MAV Control Board


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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Old 11-24-2012, 07:23 AM   #2
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No LED on 350MAV Control Board


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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Old 11-24-2012, 07:38 AM   #3
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No LED on 350MAV Control Board


Thanks for replying. Yes I meant transformer and I measured 120V to neutral.
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Old 11-24-2012, 07:53 AM   #4
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No LED on 350MAV Control Board


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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Old 11-24-2012, 07:54 AM   #5
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No LED on 350MAV Control Board


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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Old 11-24-2012, 08:10 AM   #6
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No LED on 350MAV Control Board


Let me go double check my wiring. I'll be right back.
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Old 11-24-2012, 08:11 AM   #7
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No LED on 350MAV Control Board


deleted this post after completely reading op's op.

Last edited by NiNe O; 11-24-2012 at 08:14 AM.
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Old 11-24-2012, 08:37 AM   #8
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No LED on 350MAV Control Board


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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Old 11-24-2012, 08:41 AM   #9
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No LED on 350MAV Control Board


Dont have chart in front of me ,whats 33 say
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Old 11-24-2012, 08:48 AM   #10
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No LED on 350MAV Control Board


33is open limit, so you may have a wire pulled off limit in blower compartment
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Old 11-24-2012, 08:51 AM   #11
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No LED on 350MAV Control Board


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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Old 11-24-2012, 08:53 AM   #12
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No LED on 350MAV Control Board


OK I'll go check the limit in the blower compartment.
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Old 11-24-2012, 08:56 AM   #13
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No LED on 350MAV Control Board


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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Old 11-24-2012, 09:10 AM   #14
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No LED on 350MAV Control Board


Well the old one was pretty dirty, so that's a possibility. I couldn't find the limit switch in the blower compartment. Is it the same as the rollout switch?
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Old 11-24-2012, 09:12 AM   #15
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No LED on 350MAV Control Board


Limit switch would be in the burner compartment.

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