[modernartisan]

This Nordyne Electric furnace mystery has me stumped. Hoping one of you can help figure this thing out.

The heating elements seem to work just fine. The blower motor wasn't coming on at all, even when switched to "manual" at the thermostat. I could jump across contacts on the control board and the blower would come on and run nicely, so I ruled out a capacitor problem. Then I took out the control board and inspected with magnification and found a burnt resistor. So I ordered a replacement control board and made the switch.

That seemed to solve the problem. The furnace opporated without issue and cycled just fine. But two days later it went back to the same condition. And the same resistor on the new board is now fried just as before.

Anyone out know what's going on with this thing?

 

[DOUG1111]

Put inline 3AMP fuse or breaker in from TR -- Does your board turn the blower on (relay built into board) or does board send signal to a fan relay?? Does your board send signal to a heat seq?? What does your board do?? Pic,s please. Elect furnace only?? No A/C??

 

[DOUG1111]

Be careful no to get electrocuted!!

 

[modernartisan]

The board has a 5amp fuse itself. The relays are built into the board.
I don't know about your question of signal to heat seq. System does
include A/C. It is in a downflow config. with a coil on top, air handler in the middle and heating element below that.
The fried resistor is bottom near center of the board, R21.

 

[modernartisan]

The Electroboom video is awesome. Can't wait to share it. Thanks!

 

[beenthere]

Could be caused by the blower motor itself.

 

[DOUG1111]

The Electroboom video is awesome. Can't wait to share it. Thanks!

Glad you liked the video. :vs_cool: You might try to straight wire the blower motor & check the amp draw on the motor. You can use a relay or contactor to control the blower, -you would not need to buy another board. But you need to find out WHAT (why) caused the board to burn.

If the mtr checks good. -You can check all the 24VAC switching devices one @ a time- amp clamp meter. Cheap meter/ with clamp @ harbor freight tools, around $15.00

 

[zappa]

See if you can follow the traces from R21 and determine where they go. It's in the low voltage part of the circuit so it may lead to the top connector or the blue one on the left. R21 may also be controlling Q1 just to the left of the IC's, and something external is blowing Q1 which is also burning up the resistor.

 

[supers05]

You have a system humidifier? My educated guess is a coil somewhere is starting to fail, drawing too many amps but not enough to blow the fuse.

Cheers!

 

[DOUG1111]

What was the fix??????

 

[modernartisan]

Thanks to all for your input! I disassembled everything for a thorough inspection. The heating elements all look fine. I did find a crispy relay and figure it must be the culprit. I have two of them on order. I have soldered in new resistors and am hoping nothing else was damaged on the control board. We will see.