Heater, Transmission: Operation: Operation
Coolant not required for cabin heat is directed to the transmission heater. Coolant flow is directed by a pulse width modulated ball valve located upstream of the cabin heater coolant supply. Coolant first goes to the 3-way valve inlet port. The 3-way coolant valve receives a signal from the engine controller directing to turn the ball valve in accordance with the cabin compartment heat demand. The transmission heater is an assembly containing an oil-to-water heat exchanger and a Thermal Bypass Valve (TBV). The coolant from the 3-way valve not being used to warm the cabin compartment is used to warm the transmission oil in order to get it up to the ideal operating temperature. The transmission oil flows through the cooler manifold where heat exchange from the transmission heater occurs, and then back into the transmission. The transmission oil cooler is bypassed until the transmission oil reaches approximately 82°C (180°F).