armstrong funace 7 flash

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Old 10-01-11, 09:29 AM
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armstrong funace 7 flash

Please advise.

I have 2 G2D93CT Armstrong Air Gas furnaces side by side.

The error code on one of them was 7 flashes (Lockout because of no ignition). I opened it up, saw that there was ignition and a few seconds after ignition, shut off.

Here is what I did:
  • took the flame sensor from the non working unit 1 and cleaned it. No help
  • swapped the flame sensors between the two units - flame sensor is good as it works in the other unit.
  • The flame sensor of the other unit, still doesn't work with the first unit
  • concluded that the flame sensors are good on both units
  • checked wiring - flame sensor wiring to the board below. looks good

Running out of ideas now. Don't know what else to try. please advise
 
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  #2  
Old 10-01-11, 12:29 PM
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How long does the ignition trial last before shutting off the burners?


Usually the ignition trial will be 3-5 seconds, and the gas will shut off if the flame is not detected.

The most common cause of that is a dirty flame sensor, but you have ruled that out.

The next likely problem is an ignition control that is bad and not detecting the flame. Swapping the ignition controls will test if you move that problem to the other furnace or if the problem goes away when you move the ignition control to the new furnace.
 
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Old 10-01-11, 06:37 PM
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Thank you very much for replying.

3-5 seconds and then the gas shuts off. The process repeats a few times before the unit resigns with a 7 blink code.

I am assuming by Ignition control, you mean the whole control board.

How difficult would you think swapping the boards might be? When do I get professional help and how much do you think it might cost.

Regards
 
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Old 10-02-11, 03:11 PM
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You have to judge your own abilities.

I'd move the board from the furnace that's working to the one that isn't working. If that furnace then works, get a new circuit board and install it in the other furnace.

By the time you get done doing that, you should be a pro.
 
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Old 10-30-11, 11:09 AM
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armstrong 93 furnace. 7 flashes.

After start, ignition happens, 3-5 seconds later, gas shuts off. The process repeats 5 times followed by 7 flashes.

I have two units side by side. This one is not working, its twin however is working.

Cleaned flame sensor -> no difference
Swapped flame sensor -> no difference for either unit
Swapped Control Board -> no difference fore either unit
Cleaned rubber hoses -> no difference
Swapped pressure switch (single one) -> no difference

Running out of ideas. Thinking of taking the fan down and opening up combustion chamber. It is cumbersome work, if you have any ideas for me to try, I would appreciate it.
 
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Old 10-30-11, 11:40 AM
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<< Swapped Control Board -> no difference fore either unit >>


Please describe what you did here. Your comment is vague.
 
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Old 10-30-11, 06:55 PM
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Swapped the control board from the working unit with the non working unit.

Working unit works with the board from non working unit.

Non working unit doesn't work with the board of working unit.

Regards
 
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Old 10-30-11, 07:41 PM
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check the gray flame sensor wire all the way to the control from the flame sensor. You really must check the DC microamps flame signal to diagnose the problem properly. This requires a meter that will read DC microamps.

Also make sure the burner box is grounded properly.
 
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Old 10-30-11, 08:37 PM
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Given the lack of a meter capable of reading DC micro amps, I tried to bypass the grey wire by:

- ripping open a 3 feet long telephone wire and exposing around 2 inches of copper threads on both sides

- took out the molex connector and inserted one of the exposed end into the grey wire housing/pin. Jammed the connector tight in place

- wrapped the other end of the exposed wire to the bottom metal part of the flame sensor

Essentially paralleled the grey wire to the best of my ability with a telephone wire ----- but same result. Ignition, 3-5 second hold and then shut off.

Also verified that if I disconnected the flame sensor wire from the flame sensor, the behavior is no different ----- Ignition, 3-5 second hold and then shut off.

I will go get a DC meter to measure micro amps tomorrow... but I got a question... What else might be wrong, specially if the flame sensor and wiring checks out.

Regards
 
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Old 10-30-11, 08:49 PM
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molex plug could be bad. flame sensor could be bad (doubtful). poor ground of burners, or dirty burners.
 
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