Bryant Furnace Kicking Off Intermittently

[sudhs]

I have a bryant model 398aaz060120 furnace. Everything is working fine. Gas valve is good (receives 24v). Ignitor is fine (pilot lights up). Inducer motor is fine. Gas flows and ignites. Main blower kicks in just fine and the whole system powers up without any issues. I can see the gas combustion chamber lighted up and gar burning and hot air in the vents. However, while the system is up, i hear intermittent clicks in the gas valve and whenever that happens there's loss of 24v to the gas valve and the main flame shuts off, pilot is still on though and the blower motor keeps running. Then within a few seconds, it clicks again and burners light up again. This happens every now and then at random intervals of every 10-15 seconds. The house is getting heated up and upon reaching the desired temp, the furnace automatically shuts off. Even the ignitor lockout control box LH33WZ513A seems to be working fine. Is this intermittent on-off of the gas normal ? I don't remember hearing such clicks earlier, but then I have never been near the furnace for so long. It was just today that I heard these clicks. One thing is strange that I could not locate the flame sensor anywhere on this furnace. I even opened up the gas chamber but could not see the flame sensor. I can see the ignitor and pilot assembly with the high voltage wire coming from ignitor lockout control, but no flame sensor. Any idea if the above behavior is normal AND/OR where can i look for flame sensor? Do you think replacing the 3-wire ignitor switch assembly will do the job ? BTW.. The pilot lights up fine, no issues. The burners light up fine, no issues. Don't know why this intermittent clicking and shutting off of the main gas supply.

Here's the link for the video that can elucidate on the situation https://youtu.be/bHdstCRM97M . Try listening to the clicking sound and how the gas turns on and off intermittently. Similar case as posted earlier on this forum at https://homerepairforum.com/forum/in...0-flame-sensor

[FatimaandAhmed]

It sounds like your Bryant 398AAZ060120 furnace is experiencing issues with the gas valve or possibly the flame sensor, leading to the intermittent clicking and shutdown of the burners. The clicking you're hearing is likely the gas valve closing and reopening, which can happen if the flame sensor is not properly detecting the flame or if there's a problem with the gas valve itself.

Here are some things to check:

1. Flame Sensor: Even though you couldn’t find it, your furnace should have a flame sensor. It’s usually a small rod located near the burners. If it’s dirty or malfunctioning, it might not detect the flame properly, causing the gas valve to shut off intermittently. Try cleaning the flame sensor with a fine abrasive pad or steel wool, and make sure it's properly positioned in the flame.
2. Gas Valve: The clicking might indicate a problem with the gas valve itself, especially if it’s shutting off and on intermittently. This could be due to an internal fault or an issue with the electrical connections. Sometimes, a faulty gas valve might cause the furnace to shut off and restart repeatedly.
3. Ignition Control Module: Since you mentioned the ignitor and the lockout control box seem fine, ensure all connections to the ignition control module are secure. A malfunctioning module could potentially cause intermittent problems.
4. Thermostat Wiring: Check the wiring connections to the thermostat to ensure they are secure and not causing intermittent signals.
5. Pilot Flame: While your pilot light is working, ensure it’s strong and stable. A weak pilot flame might not properly signal the main burners.

Replacing the 3-wire ignitor switch assembly might help if the ignitor or flame sensor is indeed the problem, but it's also worth addressing the flame sensor directly. If cleaning the sensor or replacing components doesn’t resolve the issue, it might be best to consult a professional HVAC technician to diagnose and fix the problem accurately.

I hope this helps!