[Chuck83]

Carrier 58PAV, approximately 20 years old. I've previously replaced the igniter, and the fan motor.

Problem: Igniter glows, gas flows, burners ignite, and the gas shuts off a few moments later. I've handled this before by cleaning the flame sensor, however this time it's different. I put a multimeter between the flame sensor, and the board, and did not detect any micro-amperage. The sensor didn't appear broken, and was able to complete a simple circuit, but I replaced it anyway. Same error after replacing the flame sensor.

Nothing has changed with wiring, no maintenance to the furnace in over a year. The ground connection is tight on the burner and gas. The flame sensor wire is connected correctly. I disconnected and reconnected the wire harness to see if it was loose or corroded, but everything looks ok.

What else can I test?
Is circuit board replacement my next action?

 

[user_12345a]

shut the gas and after the igniter glows, check ac voltage between flame sensor and ground. (modern boards do check for flame all the time, unsure of yours.


Could be a dirty burner and or plate at heat exchanger inlets.

 

[Chuck83]

Could be a dirty burner and or plate at heat exchanger inlets.

Trying to figure out how to measure ac voltage between flame sensor connector and ground...

Dirty burner or heat exchanger could cause the ignition lockout? Even if all the burners ignited?

 

[Chuck83]

Nevermind, $38 used board on ebay, and everything works again!

 

[user_12345a]

Trying to figure out how to measure ac voltage between flame sensor connector and ground...

Dirty burner or heat exchanger could cause the ignition lockout? Even if all the burners ignited?

Has to do with how it proves flame - power goes through the flame, usually to the burner.