Abstract: When a truck engine (12) is not running, an auxiliary coolant heater (32) can heat engine coolant and pump it through an occupant compartment heater (16). A coolant flow control system (10), including a valve assembly (84), associates the auxiliary heater (32) with both the occupant compartment heater (16) and engine (12) for selectively distributing heated coolant. When engine (12) has been running and is shut off, auxiliary heater (32) can be turned on and valve assembly (84) operated for occupant compartment heating while keeping the engine (12) warm. When the engine is cold, the auxiliary heater can be turned on and the valve assembly can be operated for engine pre-heating prior to starting.

Abstract: An electric heating grid extends from the middle of one side of the windshield, down that side to the bottom of the windshield, and from there across the bottom to the opposite side. The grid is operated by a control circuit having an on-off switch that is accessible to the vehicle operator. The control circuit includes a switch for sensing ambient outdoor temperature so as to allow the grid to be operated only when the outdoor temperature is below a threshold that distinguishes wintertime from non-wintertime conditions.