Bryant blower cuts on and off

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Old 10-11-13, 12:09 AM
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Bryant blower cuts on and off

Hi all,

I'm hoping someone can help me with this:

I have a Bryant (Plus 90) 350MAV furnace and I recently noticed it seemed to be short cycling. Upon closer inspection I've found that it is actually the blower turning on and off after the burner shuts off. Sometimes the blower will start and then cut off instantly, sometimes it will run from a few seconds to about a minute.
It repeats this for a while, followed by a few minutes of silence before it does it again a few times randomly. The blower seems to run fine / steadily while the burner's on, however.

I've turned shut off the power to the furnace and turned it on again, get a 12 error code, and then the LED stays a solid red with no other flashes.


Does anyone know what could be causing this?
I've done some research but have yet to come across anything that close enough to try. The closest I can get to a possible cause seems to be maybe a faulty blower relay. A lot of similar sounding cases had different fixes so I'm not completely certain.

Thanks in advance, I really hope someone here can tell me what's causing this.
Will provide more info if needed.
 

Last edited by Andromyde; 10-11-13 at 12:33 AM.
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Old 10-11-13, 04:15 PM
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<<Fault Code 12 indicates a power interruption on the furnace powered up during a call for heat. If this code is present, verify that the blower runs for ninety seconds before the furnace starts a normal heating cycle.

>>


Erratic operation of the fan as you describe is probably a defective circuit board that needs to be replaced.
 
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Old 10-11-13, 05:35 PM
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Here is a link to a guide for your unit that lists the error codes on pages 11 and 12:

http://www.gogeisel.com/geiselonline..._355MAV_OM.pdf
 
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Old 10-11-13, 07:28 PM
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Welcome to the forums.

Erratic operation of the fan as you describe is probably a defective circuit board that needs to be replaced.
Since the blower motor relies on timing from the control board to operate.... I second that diagnosis.
 
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Old 10-11-13, 07:51 PM
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Blower control lockout is the error code shown in the manual I linked. I found some in-depth steps to take to troubleshoot fault code 12: ftp://ftp.mingledorffs.com/Tech_Serv..._1993-2002.pdf

The first step is to turn off the circuit breaker for the furnace, wait 30 seconds and turn breaker back on. Then set thermostat to heat. Hopefully, that will clear the issue. If not you will need a multimeter to test voltages.
 
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