M1MB090a BW HSI question

[kberlen]

I have a problem with my furnace I need some help with. I am not a HVAC tech, but do work as an electronic tech, so I do understand some about the electrical side of my furnace. I may be in over my head with this problem. This furnace is about 10 years old, and has worked very well. We are on natural gas, and the unit has never on propane.The only problem we have had with it has been failed ingitors, which I have changed twice over this period. Most recent replacement was about a year ago. The HSI on this furnace also serves as the flame sensor.
Last Sunday, we woke up to no heat. The yellow LED was flashing, indicating low flame. Everything with the flame looked normal to me so, so I shut down the furnace, disassembled the burner assembly, and found a light buildup of what looks to be carbon on the ceramic insulator for the ignitor. I carefully cleaned this deposit off, reassembled everything, and all was OK. Steady yellow LED, and the furnace worked fine all week.
This morning, we again woke up to no heat. The red led was flashing four times indicating a lockout due to no flame. I reset the furnace, and this time had no yellow LED with a good flame. Disassembled the burner and found this same carbon deposit on the HSI again. I cleaned the ceramic insulator on the ignitor, and everything is good again.
Nothing appears to be clogged up in the burner assembly with dead bugs or spider nests. Does anyone have any idea what might be going on here? Thanks,

Kevin Berlen

[Robert]

Hi Kevin,

Not something I wish to guess at, but would advise an hvac tech to inspect furnace thoroughly.

Would be quickest and most complete way to be sure and will take some testing of burn cycles.



Thanks,
Robert