Concord90Plus Home Furnace Approx. 7 years old.

Problem:

For past 2 years during winter, temp sometimes drops below thermostat set point. In this mode, furnace compressor blower comes on, runs cycle, shuts off, but burners do not come on. After multiple cycles like this, eventually the burners fire and furnace fan comes on. House returns to set point.

In some cases, on really cold days, the temperature drops 6-10 deg below the set point before the problem "self-corrects". Then furnace may operate correctly for hours or days before the problem recurs.

In reading other internet notes, it sounds like our problem may be a dirty thermocouple. If so, how best to locate and remove to clean?

Your furnace might have a flame sensor but not a thermocouple on that new of a unit. Clean carefully but make sure it is clean. Use fine sand paper or steel wool to kind of polish it up. Below is an example of whet yous MAY look like.

Thanks for this clear response, and related pictures. I will investigate.


Your furnace might have a flame sensor but not a thermocouple on that new of a unit. Clean carefully but make sure it is clean. Use fine sand paper or steel wool to kind of polish it up. Below is an example of whet yous MAY look like.

Post back with your results