Gas furnace stays on 1 minute then shuts off -- any troubleshooting help?
I know this is an old unit, but I'd like to see if there is a fix. The T-stat in the house is set to 80, and the temp in the house is 70. The T-stat switch is set to "heat".
The blower motor in the furnace will come on for about 1 minute, and then it shuts off for about 1 minute or maybe 90 seconds. It just keeps doing this cycle. The pilot burner is constantly on, and the heater element turns on for about 30 seconds and then goes out for about 90 seconds. It also does this in a continuous cycle. There doesn't seem to be any relation between the blower motor cycle and the heater element cycle, but I'm not absolutely sure.
Here are a few pictures if they are any help. What are the 2 or 3 most obvious things the problem could be?