Grand Marquis V8-302 5.0L VIN F TBI (1984)
Coolant Temperature Sensor / Switch HVAC: Description and Operation
Thermal Blower Lockout Switch
The Thermal Blower Lockout Switch (TBL) is a combination vacuum valve and a single-pole single-throw switch powered by a thermal element. The
TBL is located in the heater supply hose in the engine compartment with the thermal element of the switch in contact with the engine coolant. In the
HEAT function lever position and with a cold engine, the blower is locked out and the outside-recirculate door is in the recirculate position.
When the engine coolant warms up to about 49° C (120° F), the electrical switch contacts close permitting the blower to operate and the
outside-recirculate door to move to the outside position.
