I have a gas-powered forced air furnace. The last time I had a repair man look at it, he said it's 30 years old, so it's getting harder to find replacement parts.
It recently developed an intermittent problem. When the thermostat switches on the heat, I can hear something turning (presumably the induced draft fan). Normally, the blower fan would start soon after that (a few seconds, sometimes as long as a minute) - but recently, it gets into a state where the blower won't come on at all, no matter how long I wait. I can make it work again by turning off power to the furnace for a few minutes, then turning it back on. But doing that several times a day all through the winter is not really practical.
Normally, I'd just hire a pro to fix it. But at this time of year, all the HVAC companies have a weeks-long backlog, so if it's something relatively simple, I'd prefer to do it myself. Any pointers on how I can diagnose this?