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dougrainer

Carrolton, Texas

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Posted: 01/11/20 11:07am Link  |  Quote  |  Print  |  Notify Moderator

I would also state wrong board. Since the P/n's were different, then the odds of a wrong board are greater. Doug

dougrainer

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Posted: 01/11/20 11:25am Link  |  Quote  |  Print  |  Notify Moderator

Here is the solution to your problem. Doug

https://www.rvautoparts.com/520839-Subur........435X85gIVUv_jBx2PegdfEAQYAiABEgL3k_D_BwE

ON THE FURNACES:
521099 CAN REPLACE THE 520741 ON THE FOLLOWING MODELS IF YOU ORDER THE APPROPRIATE WIRE KIT WITH THE 521099 BOARD:
SF20/25/30/35/42; SF20F/25F/30F/35F/42F USE 520832 WIRE KIT
NT24/30/34SP; NT40 USE 520839 WIRE KIT
NT12/16/20S; NT12/16/20SE USE 520840 WIRE KIT
DD17DSI WITH DATE CODES BELOW 9124 USE 520612.
DD17DSIWITH DATE CODES ABOVE 9124 USE 520741.

GenoB

Parker Strip, AZ

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Posted: 01/12/20 10:58am Link  |  Quote  |  Print  |  Notify Moderator

I'm leaning towards the board. Just because your seeing 12vdc on the fan lead when its unplugged could mean a little leakage through the relay or circuit board but not enough connection to run the motor.

Since you ran a direct wire from a good 12vdc and the motor ran has to lead back to the board.

sandpaper600

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Posted: 01/12/20 12:05pm Link  |  Quote  |  Print  |  Notify Moderator

@dougrainer - I think you may have solved it! Nobody ever mentioned anything about this wiring needing changed and I bought the board from the same people. I have even had email dialog with them about this problem.

I'm curious about the info in caps. Where did you find that? I followed the link and looked around for other websites selling the 520839 kit, but can't find it.

Thanks very much for your efforts in this. I'm going to order this and I'll post back after I get a result.

dougrainer

Carrolton, Texas

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Posted: 01/12/20 01:10pm Link  |  Quote  |  Print  |  Notify Moderator

sandpaper600 wrote:

@dougrainer - I think you may have solved it! Nobody ever mentioned anything about this wiring needing changed and I bought the board from the same people. I have even had email dialog with them about this problem.

I'm curious about the info in caps. Where did you find that? I followed the link and looked around for other websites selling the 520839 kit, but can't find it.

Thanks very much for your efforts in this. I'm going to order this and I'll post back after I get a result.


It was simple. You stated the original P/N and the replacement. I went to my sources and NONE had the correct older replacement. BUT, the replacement you purchased did NOT state it would work for a SP model. ONLY S model. This was confirmed by various part suppliers. THAT raised a red flag for me. So, I researched and found that your new model required a extra wire kit. The caps was because that is how I copied and pasted when I found the solution. Once I found a supplier that listed the correct SP board(your new board) it stated you had to have the wire mod kit. If I was at work, I would have called Suburban and asked what was the correct Board number and they would have told me with the proviso to get the wire kit. Doug

Per Suburban, you need the wire kit because you have 2 fan relays interfering with each other. A Time delay and the built in on the module board. The wire kit goes around the time delay relay.

* This post was edited 01/13/20 12:49pm by dougrainer *

sandpaper600

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Posted: 01/30/20 02:15pm Link  |  Quote  |  Print  |  Notify Moderator

Well, I FINALLY got this furnace sorted out. Turns out it wasn't the board after all. I was showing 12.6v on the hot wire, using the furnace chassis as a ground.

What I didn't know, until I stumbled upon it, was that there was no ground being supplied by the 3 wire connector. when I checked voltage between pin 1 and pin 2, I got nothing.

It should have been (pin1) 12v+ and thermostat+, (pin2) 12v-, (pin3) thermostat-. Instead of tearing out the couch to find the faulty wire, I ran 2 new leads from the house battery to the 3 wire connector.

What I realized afterward was the fan was only running on the low side when I hot wired it, due to incomplete grounding. When I gave it the new supply wires, the blower really spun up as it should have.

Sorry I'm so late getting back to this, but life got in my way with Dr appts and the such.

I hope this helps somebody in the future to not make the same mistakes as me :-)

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