The core of the bimetal sensor is made of 2 different types of metals bonded together, each having different temperature expansion rates. At a given increase in temperature, the shape of the sensor core changes, bleeding off vacuum available at the vacuum motor. This permits the vacuum motor to open the duct door to allow fresh air in while shutting off full heat. The bimetal sensor is calibrated according to the needs of each particular application.
- Bring the temperature of the bimetal sensor below 75°F (24°C) and apply 16 in. Hg of vacuum with a vacuum pump at the vacuum source port of the sensor.
- The duct door should stay closed. If not, replace the bimetal sensor.
The sensor will bleed off vacuum to allow the duct door to open and let in fresh air at or above the following temperatures:
- Brown: 75°F (24°C)
- Pink, black or red: 90°F (32.2°C)
- Blue, yellow or green: 105°F (40.6°C)
Do not cool the bimetal sensor while the engine is running.
REMOVAL & INSTALLATION
- Remove the air cleaner housing lid to gain access to the sensor.
- Disconnect the vacuum hoses from the sensor. It may be necessary to move the air cleaner housing to accomplish this.
- Remove the sensor from the air cleaner housing.
- Installation is the reverse of the removal procedure.