Carrier model 398AAZ036060 flame sensor

[sudhs]

Very similar case. 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 second it clicks again and gas lights 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 ir 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 gas burns 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/YAdUPaByjyM . Try listening to the clicking sound and how the gas turns on and off intermittently.

[machinist]

It sounds like you’ve got a bit of a tricky situation with your furnace. Based on what you’ve described, it seems like the intermittent clicking and gas valve shutting off might be due to a few potential issues. Here’s a friendly rundown of what might be going on and what you can do:

1. Flame Sensor Issues:
   • You might have a dirty or faulty flame sensor. This little component helps the furnace know that there’s a flame burning. If it’s dirty or not working right, it can cause the gas valve to shut off and on. It’s usually a metal rod near the burners. Try cleaning it gently with some fine sandpaper if you can find it.
2. Gas Valve Problems:
   • The gas valve might be acting up. If it’s not working consistently, it could cause the gas to turn off and on randomly. Checking the valve and making sure it’s functioning properly might help.
3. Control Board Issues:
   • The control board (the part you mentioned, like the ignitor lockout control box) could also be playing a role. Sometimes, these can send erratic signals that affect the gas flow. If everything else checks out, it might be worth taking a closer look at this component.
4. Finding the Flame Sensor:
   • If you haven’t found the flame sensor yet, double-check around the burner area. It’s a small metal rod that might be tucked away but is crucial for keeping the flame going.
5. Consider Replacing Parts:
   • If you’re still having trouble after checking these things, it might be worth replacing the gas valve or the control board. Sometimes, even a small issue with these parts can cause the kind of behavior you’re seeing.

If you’re unsure about any of this or don’t feel comfortable checking these parts yourself, calling in a professional HVAC technician might be the best bet. They can quickly diagnose and fix the issue, ensuring everything’s working smoothly and safely.