Furn. Manufactured in 1982. 1 month ago furnace kept running even though temp was satisfied. Replaced battery. I had to shut off the circuit breaker to stop the furnace from running. Turned circuit breaker back on and has seemed to be running okay. Today, when the thermostat was turned off, I was in garage and noticed the furnace door/panel was very warm. Opened door and coils were red hot inside but fan was not running. What does this mean? Any help is appreciated---Bonnie

Sounds like the relay for the coils is sticking. This can be dangerous as it can overheat the whole furnace as you noticed.

This is really an HVAC issue. I's have an HAVC guy out to look at it. It is highly doubtful that this is a DIY fix.