Carrier gas furnace inducer motor control board problems


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Old 01-27-14, 06:24 PM
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Carrier gas furnace inducer motor control board problems

Hi guys, newbie first time poster here.

I have a Carrier gas furnace, model# 395BAW036060. The draft inducer motor stopped working and I soon learned there was no power being fed to the motor. By physically touching what I'm assuming is a relay box on the inducer control board, the motor would begin working. The local furnace parts place told me the answer was simple: replace the inducer control board. They sold me a part# 313680-751 made by Replacement Components Division.

I had an HVAC technician/friend come over and install it as per the directions in the board kit. (he only had to swap out the female spade connector clip on the brown wire to a slightly larger size) Within 5 minutes we were ready to test the new part. It didn't make any difference. The inducer motor does not come on when there is a call for heat and therefore, the furnace won't run. He told me the board had to be defective and to get another one. I took it back to the parts retailer the next day and they told me "NO RETURNS ON ELECTRICAL PARTS". After much griping, they gave me another board and said they were going to have to eat the $164 for the board they just gave me. They said that for all they knew, something else wrong with my furnace could have blown the first new board out and that's why their policy is as such.

Anyway... I guess my question is: Did they sell me the correct replacement inducer board? There are a lot more little doo-dads on the new board than the old/original one did, but I figured this was because it may be some sort of a universal part, fitting a few other models. The physical board itself is the exact same size & shape, and all harnesses that connect to it fit precisely as they should. It mounts up just like the old board, fits perfect. Just doesn't work. Now I'm afraid to install the new-new board for fear they're right about there being something else wrong with my furnace which hurt the first new board. The first new board doesn't appear damaged. e.g. no burn spots, no funny smell came from it, wasn't hot on removal, etc. Any ideas what I should try? Thanks in advance!!
 
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Old 01-27-14, 06:47 PM
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Welcome to the forums.

That is a fairly old furnace. Next to no info available on it.... not even from Bryant direct.
I looked at that board... it appears to be a low voltage board that has a relay on it that operates the inducer. That board looks to run on 24vac. If that is correct..... do you have the 24vac present ?

Without seeing a schematic..... my help will be limited.
From what I can find..... that appears to be the right board.
 
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Old 01-27-14, 08:03 PM
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Thanks for the prompt reply, PJ! I really appreciate your input. Yes, it runs on 24vac and it is present at the connector coming off the furnace's harness.

Yes, the furnace is old. Circa 1987 according to the date code on the model number badge.

The original board has what appears to be one relay and one resistor on it. The new replacement board has a ton of stuff on it, despite being the same size as the original. Here's the new board on Amazon:

Carrier Bryant 313680-751 Inducer Control Board: Amazon.com: Industrial & Scientific

I don't have a schematic for the original board, but the replacement board came with multiple schematics. Would those do you any good to see?

Thanks again!
 
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Old 01-27-14, 10:12 PM
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Posting schematics would be extremely helpful. You can take large shots and post them on a pic hosting site and then leave the URL's for the fastest service. I can PM you my email address and you could send them directly to me. The board has tight limits and schematics don't post well here.

You should also have a schematic on the blower service door. It may not be useable due to the age but check it out.
 
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Old 01-28-14, 07:45 AM
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Hey PJ,

I have yet to get a pic of the schematic on the service door, but in the meantime, here's some Photobucket links to the two sheets of schematics enclosed with the replacement board:

http://i39.photobucket.com/albums/e1...ps5bfc19d5.jpg

http://i39.photobucket.com/albums/e1...psc7e09c71.jpg

If the images aren't clear enough, let me know and I will email them to you directly. Photobucket degraded the resolution of them a fair amount.

I'll get the one off the service door tonight. This is actually my mother inlaw's furnace, so I just have to make a quick trip over to her house.

Thanks again for all your help!!
 
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Old 01-29-14, 08:10 AM
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Here's a pic I took of the schematic on the backside of the furnace's blower door.

http://i39.photobucket.com/albums/e1...psb8270e95.jpg

Please let me know if you can't see enough detail with these uploads. I really appreciate all your help!!
 
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Old 01-29-14, 08:58 AM
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Temporarily putting aside the compatibility question...you say in #1 that touching the relay got the inducer spinning. Do you mean literally a light touch--or more of a tap? If just a little pressure on the plastic cover fixes the problem it's likely the issue is a cracked solder joint on the pcb under the relay. If you can re-flow the solder connections it may work fine for another 20 years.

That replacement board looks to do a lot more than the original one. Maybe a time delay has been added to insure the burners don't come on until the inducer fan is running at full speed? Your schematics are technically wiring diagrams and don't offer any clues to what is happening on the control board or the new inducer relay board, and I don't have the experience to offer more than an educated guess.
 
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Old 01-29-14, 10:29 AM
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Hey guy!

Yes, when I physically touch the relay (apply a light downward pressure), the inducer motor fires up. Shamefully, i must admit at this point that I have a small plastic bottle cap lightly wedged between the relay case and the edge of the board box. I did this as a temporary fix until I can verify I have the correct replacement board. I didn't want to install my second "new" controller board until I was certain. This way, I would be able to use it as trade-back value against possibly needing a different one.

When I had the original board off (the same one that's now back in and functioning with the aid if a plastic bottle cap/wedge), I carefully scrutinized the board and its few soldered-on components looking for cracks or broken solder. Found nothing obvious wrong. Maybe now that I know the culprit component, I should remove and more carefully re-inspect the board.

And to add more potentially needless detail, my inlaws (who's furnace this is) are getting an entirely new furnace in about 60 days. So, I'm trying not to get too crazy with the repair investment total.
 
 

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