Bryant 383 KAV furnace: inducer motor constant on


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Old 10-18-16, 11:24 AM
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Bryant 383 KAV furnace: inducer motor constant on

Hi all,

I have a Bryant 383KAV heater that I am having an issue with. Last year I woke up to a cold house and went down to check the heater. I don't remember what state the blower and inducer fan were in, but I do remember getting a code 21. I shut everyhting down, turned off power, opened it up, cleaned it out, checked all the connections and started it back up. Everything was fine and the unit fired like normal. I did some research on code 21 and thought there may be a gas valve problem and if it happened again I would have to adress the problem. It didn't, until now .

We had a few cold days so I decided to turn on the heat to check everything out. It fired up a few times wihout any problem. The other day I was in the basement and heard a fan running. I went to check it out and it is the inducer fan. I turned off the system at the thermostat but the inducer fan didn't stop running. I also noticed the code 21 again. I shut off power to the system and opened it up, clean it out and looked for any loose connections. This time, however, when I applied power to the system again, the inducer fan starts running immediately (even though the system is off at the thermostat) and code 21 starts blinking immediately. This has happened several times.

So I am a little confused. I can't troubleshoot anything because the furnace seems to be "stuck" in this state. Either the error code ins't clearing when power is removed (how?), or something is shorted and causing the error immediately upon application of power. With the fan running constantly I am thinking there is a short in the relay on the control board but I am not sure how to test. Any help would be appreciated. Thanks.
 
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Old 10-18-16, 12:20 PM
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When the thermostat calls for heat, the ignition control module closes a relay that sends 120 volt AC power to operate the inducer motor.

When the thermostat switches off the heat, that relay on the ignition control should open and shut off power to the inducer motor.

The thermostat calls for heat by switching on 24 Volts AC to the W terminal on the ignition control module. You should use a multimeter to verify that the thermostat is shutting that voltage off while the inducer motor continues to run.

Or you can disconnect the wire to the W terminal to see if that shuts off the inducer motor.

But it sounds like you have a defective ignition module that needs to be replaced.
 
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Old 10-18-16, 01:24 PM
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But it sounds like you have a defective ignition module that needs to be replaced.
How would i verify it with a multimeter if it is running constantly? If there is a short won't I see 24V there at all times?

Is the ignition control module the control board (the whole unit)?
 

Last edited by edged1g; 10-18-16 at 01:57 PM.
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Old 10-18-16, 07:40 PM
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Welcome to the forums.

Hmmmmm...... posted wrong model number info.
 

Last edited by PJmax; 10-19-16 at 09:57 AM.
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Old 10-19-16, 07:05 AM
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Pjmax,

Thanks for the welcome. I appreciate the comments but I think you have the wrong furnace model. Mine is a much simpler 383KAV model. There is a guide here.

http://dms.hvacpartners.com/docs/1009/Public/00/SP04-62.pdf
 
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Old 10-19-16, 10:03 AM
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Ok... let's try that again.

When you disconnect power from the furnace the codes are cleared. Fault code 21 cannot be set until the furnace is actually to the point of the burner lighting. Since you're getting it right from the start.... I would agree the board is defective.

On many furnace the inducer will run continuously if there's an open safety sensor but you would not get the fault 21 code.
 
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Old 10-19-16, 11:02 AM
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Thanks for the response. It makes sense that it can't throw a code 21 without actually trying to light. I'll replace the board and report back.
 
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Old 10-21-16, 02:38 PM
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I was able to get a hold of a second board. It isn't new but it was verified working in another heater. I swapped all the connections over to this "new" board and it is exhibiting the same behavior. Just to make sure I am not crazy and I am describing the code correctly, I made a short video. In the video, I have all the covers off and the click you hear is me closing the switch for the door. Please let me know if you need more detail. I am not sure what to do next.

Video
 
 

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