Wax Thermostat With Electrical Heater Element

The increased wax temperature provides higher Engine Coolant Temperature (ECT) during part load conditions and at low speed cycles. The increased ECT results in reduced friction in the engine, improved combustion in the cylinders and reduced fuel consumption and emissions. The wax thermostat heater element assembled within the wax element, regulates the ECT during high load conditions and speed points. This protects the engine from thermal overload.

Opening of the wax thermostat is at a temperature of 105°C +/- 2°C (221°F +/- 4°F).

Operation of the wax thermostat is controlled by the Powertrain Control Module (PCM) upon the following inputs:

• Engine load
• Engine speed
• Vehicle speed
• ECT
• Intake air temperature.

The wax thermostat has a battery feed from the Battery Junction Box (BJB) and a switched power supply from the PCM relay. The wax thermostat is also provided with a hardwired connection to the PCM and a ground connection. When the PCM starts to regulate the system, the PCM supplies a ground path for the heater element in the wax thermostat.

The wax thermostat is CLOSED at temperatures below approximately 82°C (179°F). When the engine coolant temperature reaches approximately 82°C (179°F), the wax thermostat starts to OPEN and is fully OPEN at approximately 96°C (204°F). In this condition, the full flow of engine coolant is directed through the radiator.