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Discussion Starter · #1 ·
Hi, we came home on Christmas Eve to a burning plastic smell in the house. Thought it was the Christmas tree, so I unplugged it, ventilated the house, and we went to bed.

Next morning, got up, heat wasn't working and the smell was back. Traced it back to the control board on the (natural gas) furnace. Here is what it looks like now:

https://drive.google.com/file/d/0B8PTN77UH_WWTzJFcW1JbHNfd1U/view?usp=sharing

You can see the board itself is burned at the bottom, as well as some of the wires. We had an HVAC tech come out and diagnose it, this board was the only issue he found (other components such as inducer and blower tested OK), but they wanted $737 for the repair; and, they didn't even have the parts yet, so we'd still be without heat for a few more days.

The control board is a "62-24268-01 / 1012-925A" which I found what appears to be a newer replacement, 62-24268-03 / 1012-925C, on Amazon for around $105 and it will get here on Monday.

I am pretty confident I can replace the board itself easily enough. My concern is with the wiring harnesses, I'm having trouble finding these things online and of course all the local HVAC distributors/stores are closed. Does anybody know a good source for these things?

Also, I notice the old board has DIP switches (top right corner) and the new board has a set of jumpers there instead, so I guess I'll have to "translate" the DIP switch settings to the jumper settings. Has anyone does this before, and if so, did the board come with instructions for this or will I have to get a multimeter on it and test my way through it?

Any other caveats to watch out for, or any other tips?

Thanks!!!
 

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it should come with instructions. those dip switches are usually for setting the amount of time in seconds the fan runs when the heat shuts off. the factory settings are usually OK.

I would carefully remove those wires one at a time and check for damage on the pins in that connector. It may just be smoke and not melted. If so you can clean it and re-use it. That wiring harness may be special order as it is rare one is sold or needed.
 

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Discussion Starter · #3 ·
Thank you Yuri! That is a great idea, I hadn't considered NOT replacing the harnesses/connectors. I'll check them out as you suggested. And if any of them is damaged, maybe I can repair the wires individually... I am awful at soldering so I was hoping to be able to get away with not doing any of it, but I guess I will need to do some practicing this weekend.... :(

For the wires that did get burned, I was going to splice the smaller-gauge wires (which I assume are low-voltage) outside of/above the plastic wiring box with a spade connector. And there seems to be 1 larger-gauge wire which connects directly to the blower, that is cooked, so I assume I'll have to splice in and solder a new wire there. I will ask the guys at the store for insulated wires for this application, but I assume I will also need some kind of heat-shrink insulation to cover up the soldered splice?
 

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You don't need to solder wires. I don't. Use a barrel/tube type splice connector. It has a metal insert and you stick your 1/8 to 1/4 inch of bare wire in both ends and crimp it. Or use wire nuts. Radio Shack should have both or some auto parts stores along with a wire stripper/crimper.
 

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Discussion Starter · #5 ·
Thank you again. Is it OK to do that kind of splice inside the control board box, i.e., is it safe for that kind of usage (where there could be high heat or even small flames if another board cooks)? Or do you just mean for the low-voltage splices outside the box?
 

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you can use them anywhere. they come in different wire sizes. # 18, 16, 14 etc make sue you use the right size
 

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Discussion Starter · #7 ·
Hopefully this is my last question. :) I think I'm ready to buy the small connectors I need.

I need to replace connectors on 5 wires: 2 going to a relay, 2 going into the harness, and 1 going to the blower.

The blower and relay wires have enough slack in them that I shouldn't have to splice an extension into them, I will just replace the female blade connectors.

The harness wires will need a little extra length, so I'll use butt splices to extend them.

All of them have blade connectors, insulated on the relay and harness connectors and uninsulated on the blower wire connector.

I think the (white) blower wire carries line voltage, although I haven't tested it now that I have the control board removed, wires cut, etc. -- the adjacent, similar terminals are just crimped on, but this one is melted pretty badly so I can't tell if this white one was soldered in addition. Some of the strands are gray, so I'm not sure if that's melted solder, or some kind of heat damage. Should I solder this one (in addition to crimping on the new terminal), or is it OK to not solder it even if it does carry line voltage?

Here's what it looks like: https://drive.google.com/file/d/0B8PTN77UH_WWMEFWX1ZCN2hMVnc/view?usp=sharing
 

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Discussion Starter · #8 ·
Also, just ran into an issue... the wiring diagram inside the box shows the following wiring, in this order:

Heat: Blue
Cool: Black
M1: Red

However, my written notes and my photos clearly show the Heat and M1 reversed vs. what's in the diagram, so they were set up as follows:

Heat: Red
Cool: Black
M1: Blue

Looks like the M1 is supposed to be the Unused Motor Lead. When I get my new board, would you recommend installing it per the diagram (which is clearly different from the way it was on the old board), or just installing it the same way it was before? Everything seemed to be working fine previously, so is/was it harmless to have those wires reversed?
 

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Hi GMX, I'm sure it wasn't soldered from the factory however make sure that all of your repair crimps are good and tight. A loose connection, most likely between a spade and lug or the solder connection to the board, is what caused this heat damage.

I would wire the blower like it was and not according to the schematic. The install tech probably did that to lower the air flow for the heat cycle. You could take some measurements and adjust it later if you want to check the accuracy.
 

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A crimping tool with jaws shaped like this give the tightest crimps but in most cases your replacement lugs need to be straight and not 90 degree for the tool to fit without crushing the rest of the lug.

You may want to check the blower motor to make sure it spins freely and is not drawing too much current as it could have contributed to the damage.

 

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White wires are always neutral and never carry any current.

Just use ordinary straight 1/4" spade connectors wherever you can. Don't really need angle ones unless a straight one won't fit.

Red is the low speed wire. Not sure why someone would want to use it for heat as it may overheat the furnace. Check the temp rise to see if it is safe. Stick a cooking thermometer in the duct one foot downstream from the plenum after it turns horizontal. Must not see the heat exchanger. Subtract the house temp or return duct temp and then look at the rating/model sticker for the temp rise. ie: 30-60F
 

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White wires are always neutral and never carry any current.

Just use ordinary straight 1/4" spade connectors wherever you can. Don't really need angle ones unless a straight one won't fit.

Red is the low speed wire. Not sure why someone would want to use it for heat as it may overheat the furnace. Check the temp rise to see if it is safe. Stick a cooking thermometer in the duct one foot downstream from the plenum after it turns horizontal. Must not see the heat exchanger. Subtract the house temp or return duct temp and then look at the rating/model sticker for the temp rise. ie: 30-60F
Thanks for adding the temperature rise information Yuri. There is the same amount of current on the neutral as the hot in this case.
 

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Discussion Starter · #13 ·
Hi guys, I need to run out today to pick up some wire to splice into the harness. I've gotten the specs off the wire and found the following:

• Style 1275
• 600V
• VW-1
• 60 C moisture resistant
• 105 C heat resistant
• 18 AWG
• AWM
• CSA AWM 105 C
• FTI

(Made by Tennessee Wire & Cable Co.)

Not being an electrician, I had to look up some of that stuff. First I thought I'd IDed the wire as THHN or THWN, and then XHHN, but now I think I've found exactly the specification I'm looking for:

Style 1275: http://data.ul.com/link/stylepage.aspx?style=1275

Seems like the "Big Box" stores around here (Home Depot, Lowes) don't carry this, at least not in 18 gauge. So I'm calling around to local electrical suppliers.

If I just call and ask for "Style 1275" (in 18 ga.), is that the proper operative term to get on the same page with these guys? I just talked to one supplier who seemed clueless, so I'm not sure if I need to be calling it something else. The UL listing seems pretty straightforward in that all the requirements (heat, wet, etc.) are called out as requirements for this "style" so I thought that was an easy way to get straight to the point.
 

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wire type does not matter. ideally you want stranded wire not solid so it can flex. check radio shack as they may have rolls of hobby wire. you can go up in size to #16 or #14 as well. just not lower than #18 ie: #20
 

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Discussion Starter · #15 ·
OK, I've already got a couple spools of "plain" 18-ga. wire that I can use then. May not be the right colors, but I can swap it out later. I was just concerned about the heat and moisture resistance.

I made some more calls around today and it seems like nobody knows what I'm talking about when I ask about "Style 1275" wire. :huh:

Well, here we go then... also I intend to wire this thing up "correctly" as per the wiring diagram, i.e., "fix" the reversed Heat and Unused leads on the blower.

Zappa, I checked the blower motor rotation too as you suggested, and thankfully it spins smooth as silk. Thanks for the tip. :thumbup:
 

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Discussion Starter · #17 ·
Just want to update this thread and also thank everyone again who helped out! I installed the new board this past Monday, and everything's been working fine so far. I did end up connecting it as per the wiring diagram; I intend to do the heat rise test as soon as I get a chance, hopefully this weekend. Also I ended up not having to splice that wire, there was enough slack in it where I didn't need to (without having the wire stretched too tightly).
 
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