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I had to replace a honeywell ST9120C 4057 control board last…

Customer Question
I had to replace...

I had to replace a honeywell ST9120C 4057 control board last spring. My heat didn't come on today and its the first day I've used it this year. Im assuming that something wasn't reconnected properly when i exchanged the control board. My Ignition system controller Honeywell S8610U has voltage coming to the terminals 24VAC.. but i don't have an active status LED. The manual for the ignition module states that no LED means that its not calling for heat. What do i test or check on the control board to ensure it is calling for heat?

Contractor's Assistant: Did you double-check the thermostat's settings? And what about the filters?

Yes, both seem to be good. I do have 28.3 VAC on the W, & R terminal on the control board testing from the common

Contractor's Assistant: Do you plan on doing the work yourself?

Yes, I am a master electrician

Submitted: 7 months ago.Category: HVAC
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Answered in 1 day by:
12/10/2017
HVAC Technician: Kcrand36, HVAC Mechanic replied 7 months ago
Kcrand36
Kcrand36, HVAC Mechanic
Category: HVAC
Satisfied Customers: 80
Experience: Owner at Advantage Repair
Verified

Good morning, I am Kevin, one of the tech's here on JA. did you test the voltage across R and W? Or just R to common and W to Common?

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Customer reply replied 7 months ago
Easy money for you today. I repaired the unit 5 minutes after I paid for your service.
HVAC Technician: Kcrand36, HVAC Mechanic replied 7 months ago

well, not for me.... lol. as the technician, we do not get paid until you leave us a rating for the service. But I am glad to hear that you fixed it. What was the solution? Many times, customers don't get back to us, and we really like to know what solved the issue.

Thank you for responding

Happy Holidays

Kevin

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Customer reply replied 7 months ago
Several things that I did . Not sure if any or all helped. I found the polarity reversed where the pigtail attaches to the air handler. I found that the frame ground was terminated at the 24VAC ground on ignition controller ... and the yellow from the main controller was connected to the 24VAC terminal at the ignition controller . Removed ground and put yellow wire on the 24VAC ground terminal.
Customer reply replied 7 months ago
A friend that was supposed to be versed with HVAC helped
Me troubleshoot the main computer troller last spring. I think he didn’t put things back correctly
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