Arcoaire Furnace - Bad Control Board?


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Old 11-07-10, 04:29 PM
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Arcoaire Furnace - Bad Control Board?

I have been having issues with my Arcoaire furnace (see Arcoaire Furnace Overheating thread below) so I decided to clean it good today. Here is what I did:

1) Pulled burners and cleaned them with a brush and blew them out with air (just a few hole blocked with rust, cleaned out easily)
2) Blew out with air and vac'd out the burner chambers (very little debris/soot)
3) Cleaned the flame sensor
4) Pulled the cover off the secondary heat exchanger and vac'd it out and then blew air through each tube while the vac was on the ID output to catch soot
5) Pulled the blower motor and blew the dust off each fin and oiled it

I put it all back together and fired it up. It ran for about 10 minutes and then totally shut down. No trouble codes, nothing. I jumped the thermostat terminals at the furnace to make sure it wasn't the stat and still nothing.

I turned off the breaker for a few minutes and then it fired back up. While it was running I decided to pull the leads off each of the safety switches to see what happened:

1) Hi-limit - burner shut off, ID and blower continued to run, gave code
2) Pressure switch - burner shut off, ID and blower continued to run
3) Roll out - inline with Pressure switch so same as above
4) Condensate - burner shut off, ID and blower shut off, gave code

It appears to me that all the safety switches are working as they should and when one kicks out the board gives a code. I am thinking my board is bad causing the intermittent problems I've been having.

ecman, could I get your thoughts?
 
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Old 11-07-10, 05:58 PM
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Some additional info:

I just fired up the furnace and it went throught the following sequence:

ID came on, ignitor came on, burners fired, CB came on. After about 30 seconds the whole thing shut down with no trouble code. I pulled one of the wires off the hi limit switch and the CB came back on and the controller gave me a hi-limit fault. I put the wire back on and the ID came back on and the furnace fired back up.
 
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Old 11-08-10, 07:18 PM
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With all you've done I tend to agree that the problem is within the board.
About the only other thing you could do is to chase the 24 & 120v to see where it is dropping out but my guess is you are going to find the problem to be the board.

EC: Your thoughts?
 
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Old 11-10-10, 04:06 PM
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I believe that Phipps must have reset the board when he disconnected, then reattached the safety circuit (limit switch). Need to know if anything in that safety circuit goes away on it's own, when it shuts down say in 30 seconds (iow, loses 24 volts from 24 volt safety wire to ground), before condemning the board.

Telling someone their board is faulty (or a gas valve is faulty), with certainty, are the two scariest things I find having to do, sight unseen, about these forums.

I just reviewed your first post in this thread where you said what stops running and what stays running when you pulled off certain safety wires. So what shuts off and what stays running, when the furnace shuts down, even when you have the thermostat wires jumped (I presume R to W). And again, what kind of ignitor do you have?
 
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Old 11-10-10, 05:24 PM
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Originally Posted by ecman51` View Post
So what shuts off and what stays running, when the furnace shuts down, even when you have the thermostat wires jumped (I presume R to W). And again, what kind of ignitor do you have?
Everything shuts down....nothing is running....and there are no trouble codes.

My ignitor is a "rod".
 
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Old 11-10-10, 06:03 PM
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Okay.

Have you tried to remove the flame sense wire on the board, to see what stays on and what goes out?

If that is NOT like your symptom, then you most likely have a marginal electrical connection or a bad board.
 
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Old 11-11-10, 12:34 PM
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Originally Posted by ecman51` View Post
Have you tried to remove the flame sense wire on the board, to see what stays on and what goes out?
I never did that as my flame sensore is "hard wired" into the connector, but according to my owner's manual, if no flame is sensed then the gas valve is shut off but the ID is supposed to continue to run to clear the burn chamber. Mine was shutting down completely.

Now an update: I was able to get a board locally through an HVAC friend of my brother's.

Put it in this afternoon and all appears to be running again!! It's supposed to get colder this weekend so we'll know for sure then!

FWIW, I pulled the back off the old board and the circuit board was burnt in a couple of spots.

Thanks for everyone's comments, hints and ideas!!
 
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Old 11-11-10, 04:07 PM
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Originally Posted by phipps33 View Post
FWIW, I pulled the back off the old board and the circuit board was burnt in a couple of spots.
I actually suggested that very thing to someone the other day, on this board. I guess we have to keep remembering to suggest that. Not that that always shows the problem. But if you see burned marks, then you can rest assured that was your problem.
 
 

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