Re: [EE]: Flame rectification

Hi Allen,

Several things are important for it to work. The gas valve has a few wires. One is ground.
There must be a ground wire from the gas valve to the control box. The control box uses that as part of the sensing circuitry.
The tubing from the gas valve to the pilot must have electrical continuity.
The pilot flame must surround the flame sense electrode and not wash too much on anything that is grounded.
If there is too much draft, it can push the pilot flame around, that's bad. Maybe the garage door has a gap and there's random airflow around the furnace.
Also the flame must be blue, if there's yellow the gas atoms have lost their charge. Hopefully you have a viewport to observe the pilot in action.
You can clean the pilot orifice with a cat or dog whisker without risk of damaging it.
I've heard that Johnson integrated gas valve and ignition systems go bad, but that's just hearsay. I have a Honeywell system with separate valve and ignition module and it's been working since 1997.

Hope this helps!
Friendly regards, Bob

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From: Piclist <[email protected]> on behalf of Allen 
Sent: Wednesday, December 24, 2025 4:44 AM


I have been working on (baffled by) my daughter's Payne high efficiency
furnace. The flame detector seems to be a simple steel rod. It has only
one electrical connector with about 90V on it. I assumed, at first, that
it was some kind of thermocouple referenced to ground through its one
mounting screw. However, the path from the connector to ground seems to
be open. Diagnostic instructions indicate that it should carry .5
micro-amps or more. It looks like the flame provides the path to ground.
It it gets dirty it doesn't work. Does anybody know anything about this?

Allen