I am having problems with one of my two furnaces. When the thermostat kicks in, the furnace will light, but the fan won't kick in. Then the furnace shuts down. If I turn off the heat (i.e. not on heat or cool), and turn the fan to "on", it just hums (the other furnace works fine and the fan will run). There is a solenoid that clicks, then the humming. The fan itself turns effortlessly.
Do you think this could be a problem with the capacitor, solenoid or transformer?
Also, I have been having another problem (probably unrelated?) once a year every winter when I first start the furnace. The fan doesn't want to kick in but I didn't notice any humming - this appeared to have something to do with that timer-like dial (is it a temperature limit switch?). Two taps with the end of a screwdriver and I'm usually OK for the year.
Any ideas on either problem? Thanks.