Need help troubleshooting furnace - igniter replaced


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Old 01-13-12, 09:55 PM
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Need help troubleshooting furnace - igniter replaced

Hi All.

I have a problem with the following furnace:
Cumberland (80%), Yr: 1990
Model: FUAD120A50B1
Control Board: White-Rodgers: 50A55-486 or CNT03797

Issue:
Igniter and burners would not come on after a call for heat.
After turning on the power to the furnace, and monitoring the control board (see model above) during start-up, the following was observed:
1. The control board would fast flash after power is turned on.
2. Unit would 'click' about four times, inducer motor would turn on, but the igniter would never glow, and the burners would not turn on.
Note: Igniter was replaced with a new one.
After 5-10 seconds with the inducer motor running, it would shut-off and the blower motor would start running. Never sounded like the gas valve opened.
3. Then, the control board would flash 6 times and then pause, indicating "115 volt AC power reversed/improper ground

I had a heating company come out, but was not very happy... they spent the whole day trying to locate a part, but called my maintenance man back asking for the part number off the control board. Then, at the end of the day after calling for a status update, I was told supplier is closed and it would be two days before they would receive the control board/harness, etc. The bottom line is that they recommended to replace the control board.

I have the control board and will attempt to replace it tomorrow, but when inspecting the furnace last evening (after putting heaters in the property due to freezing), I noticed one of the wires to the gas value was hanging and not making a good connection (see picture). The brown wire was disconnected. There was an Red, Orange, Grey, Brown, and last slot was empty. Could a bad connection with the brown wire on the gas valve be causing an issue?

If the control board does not fix the issue, I may be looking at installing a new furnace due to the age, but would like any recommendations prior to making this decision.

Thanks for your help in advance.

Pictures:
https://docs.google.com/open?id=0B9R...Q0ZDdjMGQ5MmEx
 
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Old 01-13-12, 11:12 PM
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You are describing highly erratic operation of functions controlled by the ignition module --- so a bad ignition module sounds like a very reasonable diagnosis.

Your picture is cut off with only a minimal view of the brown wire. Any poor connection should be repaired, but a bad connection at the gas valve would not explain a variety of other erratic operations of the system.

I can understand your disappointment in your service provider not locating the part faster. Frankly, shopping around for parts is a nuisance for repairman, too. It sounds like they made a reasonable diagnosis and have been trying to do a good job for you.
 
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Old 01-15-12, 02:05 PM
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Issue fixed after replacing control board

Hi. I just want to let everyone know that replacing the control module and securing the wire to the gas valve fixed the issue. After replacing the board, the igniter would glow so we knew we were in business.

Thanks for the help.
 
 

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