Why is the blower running constantly on my heater?

Answer by  rrazorbakk (62)

Either the thermostat is set to "ON" for the fan setting, or the relay controlling the blower is stuck on or the contacts are "welded" closed.

Answer by  ImtiazAhmad (74)

The blower of the heater run constantly when the controlling switch of the heater does not work properly. The other reason may be uncontrolled thermostat controller. When the atmosphere temp of the place/room does not match with the thermostat controller then the same situation may occur. In either case complete diagnostic is necessary to rectify it.

Answer by  bitsandbytes2001 (9)

The most common reason for the blower continually running on your heater is that the activation switch on the wall for fan control is set to "manual". Change the fan control to "automatic", and it should only run when it is cold enough for the heater to start running in conjunction with the fan.

Answer by  David87 (112)

Thermostat could be set to on rather than auto, furnace could be set to on rather than auto, or you could have an electrical malfunction

Answer by  mike90 (71)

Several things could be causing it, the thermostat could be set to fan "on" mode,could have a bad fan limit switch ,a bad high limit switch or if the unit is a newer model it could have a short on the control board,its best to have it checked by a professional