When Thermostat switches to Heat On, the blower won't run. 2 Days ago I could get the blower to start by just changing the Fan from Auto to On, but now the blower won't even start when switching the Fan to On. I hear the click at the thermostat when Heat kicks On and also when Fan is switched to On. I also hear some sort of click noise at furnace when Heat kicks On and also when the Fan is switched from Auto to On. I am now starting to hear a slight buzz or hum when the blower tries to turn on, the buzzing noise continues until Fan is switched back to Auto. Pilot light is on. I've done some searching online, but don't know what steps to start with to diagnose problem and then repair. I've never used a volt meter, but have replaced thermostats, repaired an electrical dryer, a dishwasher and replaced a number of light fixtures which my wife spent about $2,000 on, hence I was the laborer. So I can do the work just need the correct steps and procedures. Please help. Thanks! Joe