I have asked about a heating problem I am having with a Trane package A/C. The one that the burners come on but the fire won't stay lit.
I got an answer to that question. I was told that it may be because the flame sensor was dirty and should be taken out and cleaned.
I did that but I still have the same problem. I also did a continuity test on it and it was OK. I asked a parts supply person if he had any ideas and he told me it could possibly be the gas valve or the circuit board. I have priced the circuit board for that unit and it is very expensive ( $395.00). I don't want to buy one and then find out that was not the problem.
This is a Trane package unit about ten years old Model number; YCCO36F1MOBE
Does anyone know if there are good used boards around?
This has been a major headache for me. I am a retired HVAC contractor and it has been a while since I serviced hvac units and the ones I used to work on did not have circuit boards. HELP?

Thank you

Frank

Hmm, it sounds like a flame proving issue. If we can rule out a dirty flame sensor, then something else is compromising our flame current. The ignition control should have a solid ground path to the burner assembly-no burned or oxidized wire ends. The flame sensor rod must not come in contact with or otherwise be grounded to any metal surface. The flame that passes over the sensor must also make contact with a relatively clean metal surface. If the inlet port that the flame passes through is very rusty, flame current will be weakened. I hope you find these suggestions helpful.

A defective sensor wire will also cause this type of problem. A continuity test may not show the wire having a high impedance. As mentioned by KC13 a grounding problem can also be a cause.

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Originally Posted by KC13

Hmm, it sounds like a flame proving issue. If we can rule out a dirty flame sensor, then something else is compromising our flame current. The ignition control should have a solid ground path to the burner assembly-no burned or oxidized wire ends. The flame sensor rod must not come in contact with or otherwise be grounded to any metal surface. The flame that passes over the sensor must also make contact with a relatively clean metal surface. If the inlet port that the flame passes through is very rusty, flame current will be weakened. I hope you find these suggestions helpful.

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Thank you for your answer. I will try and check for all these things. I did clean the sensor rod and the ignitor tips were checked and cleaned also. When the stat calls for heat the I.I.D. (Ignition device) sparks and the flame does come on but as soon as the I.I.D. quits sparking the flame also quits.
Is it possible that the gas valve is bad?

Thank you for your help.

Frank

Quote:

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Originally Posted by hvac1000

A defective sensor wire wil also cause this type of problem. A continuity test may not show the wire having a high impedence. As mentioned by KC13 a grounding problem can also be a cause.

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Thank you for your help. I have to keep going on this problem until I find the problem. This has always been my nature. "Never give up", is my motto.
I will write and tell you if changing the gas valve solved my problem.
The part that baffels me the most is that when the ingnitor stops clicking the fire goes out. There is a flame there, up until that moment.

Thanks

Frank