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Old 11-17-2011, 06:33 PM   #1
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Yuri


Had a G71mpp-36C-090-03 today with an Icomfot stat, error code locked out on flame loss. Cleaned flame sensor,burners and crossovers and it fired right up. Checked flame signal and it was bouncing all over the place. Checked voltage from fs terminal on control board to ground and it was rapidly fluctuating between 2.8v to 36V. Tech support said it should be constant. Grounds checked good so I replaced the board which still did the same thing. 0V between C and ground,steady 28V from transformer.

Never saw anything like that before and am at a loss. Was tech support wrong and the G71 with Icomfort actually fluctuates the voltage or is it supposed to be steady? Furnace works but I don't like funky readings.

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Old 11-17-2011, 06:45 PM   #2
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Yuri


Rms meter.

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Old 11-17-2011, 06:48 PM   #3
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Yuri


You cannot check the flame signal on a G71 or SLP with a microamp meter the conventional way we do it. There is a special procedure you have to follow with the self diagnostic features/buttons on the board. I had some tech training when they first came out and the trainer told us the right away. If you still have DaveNet there should be a complete service manual on it. Has more in it then the install manual. I will look into it myself as I have not had to do it yet. Had to use those diag buttons and they are tricky. Have to hold your mouth and head the right way when using them.

Some of those tech support guys need to read their manuals too. You CANNOT add any load to the W terminal on a SLP or with the IComfort (like a humidifier) must use a extra relay or the hum terminal or eac terminals.

Field Test Mode. P19 in the service manual. Has it in fine print on the wiring diagram too.
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Last edited by yuri; 11-17-2011 at 06:58 PM.
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Old 11-17-2011, 06:48 PM   #4
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Yuri


Certain voltages such as a hsi are sent in impulse. The rms averages these readgs.

Ill shut up now.
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Old 11-17-2011, 06:56 PM   #5
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Yuri


You are trying hard and have a good attitude. They recommend True RMS meters for the new high end boards and I have one.
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Old 11-17-2011, 06:57 PM   #6
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Thanks yuri.

Doc you're going to get the foghorn leghorn treatment.

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