Carrier 58MWP Weathermaker furnace fault code 34


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Old 09-17-21, 12:58 PM
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Exclamation Carrier 58MWP Weathermaker furnace fault code 34

Heat cycle failure with fault code 34. Inducer motor does spin up for many seconds, I hear a click, then failure with the LEDs showing 34. I never see the igniter glow. I put a meter on the igniter connector and don't see voltage. Was expecting it after that click. I did recently install a new igniter, hoping that was the problem. It still shows continuity, no short. Of course, no voltage to it, so it shouldn't be the problem. Limit switch also shows continuity. Gas switch is ON. Blew out all vacuum tubing, which seems ok. I'm still hoping it's not the control board.
 
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Old 09-17-21, 05:47 PM
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Welcome to the forums.

I put a meter on the igniter connector and don't see voltage.
On a call for heat......
1) the inducer starts running.
2) after typically 10-15 seconds the pressure switch proves ok.
3) you may hear a faint click. That is the relay turning on the 120v igniter power.
4) you should have a meter connected to the igniter plug with the igniter plugged in. If you don't get 120vAC then the igniter relay has failed and the board will likely need to be replaced.
 
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Old 09-17-21, 06:53 PM
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Thanks, Pete. I tested without the igniter attached, just inserting the meter probes into the wire connectors. No voltage measured. So I need to retest with the igniter attached, too? I'm a klutz at this! Is there a way of testing at the other end of the igniter wire, at the control board? I saw instructions to remove PL4 from the control board, but I don't know where to find that. Nothing is labelled. Then test across PL4-1 and PL4-2, if I can ID those. The control board is HK42FZ012. If you think it's worth testing like this, would you please show me where all this PL4 stuff is.
 
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Old 09-17-21, 07:43 PM
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Look closely at the board.... the ends of the plugs.... they are labeled.
If you don't get 120v at the igniter plug then it's not coming out of the board.

There should be a wiring diagram on the back of the blower door.
I'd need the complete furnace model number to find a wiring diagram.
The ID tag is on the side wall near the burner.
 
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Old 09-17-21, 09:00 PM
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If you open and scroll done to "error 34" you should get some checks to make. carrier_variable-speed_2-stage_troubleshooting.pdf (graycoolingman.com)
 
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Old 09-18-21, 10:25 AM
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Thanks you guys. The control board's plugs are hard to get to due to the surrounding housing. Rather than mess with it, I will bite the bullet and order a new control board. I will update this thread after receiving and installing it. I may have a new control board for sale if this doesn't do the trick, but we'll see. Thanks again and see you back here in about two weeks.
 
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Old 09-24-21, 03:26 PM
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I got the new HK42FZ012 Rev F control board a few hours ago, managed to remove the old one with numerous photos of what wire goes where, installed the new board and it looks like all the wires were done right ,,, it works! My first clue back on the original problem was an igniter not glowing, testing showing no power getting to it. When that glowed today, my hopes were on the rise. Burners lit up, fan was modulating itself, and, eventually, heat!

Thanks so much to Pete and fastback. I felt like you guys were there to help me up if I fell, which could have easily happened. Many thanks.

One last note on this board: mine was a Rev F. I found many HK42FZ012 boards out there, but most had a lesser rev level. Not even sure how they might have done. Some were cheap, used boards. But had I gotten one of those to try and it didn't work for some reason, well, you don't know what's wrong, the board or still something else that you'd overlooked.
 
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Old 09-24-21, 04:13 PM
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Control board innards

Popped open the old control board case and got the board out. No visible signs of burning. Back side, too, looks ok.


 
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Old 09-24-21, 05:58 PM
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Installing used parts is an excellent way to heat your home on a weekend until you can get a new part. Same thing with trying to do repairs on a control board. The one exception would be when something goes obsolete or you have a secondary source of heat. Risking frozen pipes just isn't worth it, I know. Your board, lacking anything visible, likely has a stuck, sticky, or dead relay. Glad your all set now.
 
 

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