My Trane TWG018A140B1 Blower Will Not Shut Off

Extreme Set Point

• Your blower will continue to run if the temperature setting is too high or too low. The blower only shuts off once the desired temperature is reached. Your thermostat controls the desired temperature setting. If you set your thermostat to 45 degrees on a hot day, the Trane system cannot reach that temperature, which prevents the blower from shutting off. If you set your thermostat to 95 degrees on a cold day, the opposite effect occurs, but the blower will continue to run, because the Trane system cannot reach the desired temperature setting.

Fan

• Your thermostat has a button that sets the blower to "fan" or "auto." The fan setting will cause the blower to continue to run even if the desired temperature has been reached. You need to set the button to auto, ensuring the blower will shut off automatically, once the Trane system reaches the temperature setting.

Faulty Thermostat

• A faulty thermostat can prevent the blower from shutting off, as well as the entire Trane system. If the thermostat does not operate properly, the heating and cooling system is not being controlled properly. A short in the thermostat can affect the temperature setting, cause the setting to fluctuate, or not register any temperature setting. Most of the time a faulty thermostat will cause the entire system to shut down, but it can prevent the system, including the blower, from shutting down.

Limit Control Switch

• Some Trane systems use a fan limit control switch if the thermostat does not have a fan setting. These switches control when the blower turns on and off. A faulty switch causes the blower motor to run continuously. The switch also prevents the blower from running at all. Most of the time, the last setting of the limit control switch will be maintained when it fails. If the blower motor is running when the switch fails, it will continue to run.

Electrical Short

• A short in the electrical system will also prevent the blower from shutting off. Each blower motor has a junction box on the side of the component. The junction box is the connection point of the control wires. A short is one of these control wires causes the blower to run all the time. When the blower is required, voltage is sent to the motor, powering the component. Once the blower motor is no longer needed, voltage is disconnected from the blower motor, shutting it off. If the disconnect contact short circuits or melts in the closed position, voltage will continue to flow to the blower motor.