Electric Thermostat

The electric thermostat allows rapid engine warm-up by preventing coolant flow through the radiator and by limiting coolant flow through the cylinder block when the engine is cold. During warm-up and at engines speeds above approximately 1800 RPM, a by-pass valve opens to control the coolant flow and pressure to protect the engine components. When the electric thermostat opening reaches 6 mm (0.24 in.) the bypass flow is shut-off. When the electric thermostat opening exceeds 6 mm (0.24 in.) the radiator coolant flow is further controlled up to the point where the electric thermostat is fully open. At this point maximum radiator coolant flow is achieved to provide maximum cooling.

The electric thermostat begins to open at 103 - 105 °C (217 - 221°F) and is fully open at 119 °C (246 °F).

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

• Driving style
• Terrain Response® mode selection.

The electric thermostat heater allows to the PCM a decreased opening temperature at 85 °C (185 °F). This causes the element to expand and increase the opening dimensions of the electric thermostat.

The electric thermostat has a switched power supply from the PCM relay, located in the Engine Junction Box (EJB) and a hardwired connection to the PCM. If the PCM starts to regulate the system, the PCM supplies a ground path for the electric thermostat heater.