| Heat and A/C usually use a different winding in the motor controlled by different relays. For heat, the blower is also controlled by a limit switch. The blower doesn't come on until the limit switch warms up and closes. So the problem could be the motor itself, the relay, or the limit switch, or some of their wiring. Most often it is the relay, and on most newer systems it is on a circuit board, hard to diagnose and replace except by a very expensive new board. While you are working on the problem, you may be able to get some heat using the fan on switch at the thermostat. |