Abstract: A convienience feature is added to a DRL circuit to enable the driver to temporarily override the DRL system in situations where it is appropriate, such as when the vehicle is approaching weigh scales or entering a tunnel. The convenience feature is embodied in a convenience circuit that is interposed in the current feed path to the DRL circuit. The convenience circuit comprises a momentary switch that is actuated by the driver and a timing relay module that is responsive to the actuation of the momentary switch.

Abstract: A parking lamp operating system reduces the electrical load on the battery of a vehicle, such as a truck, during periods when the vehicle engine is off but the parking lamps of the vehicle remain on wherein a switched signal input from the battery is modulated to provide a pulse-width-modulated output to the gate of a power transistor having a power input from the battery and an output to the parking lamps. The pulsed signal causes the transistor to intermittently switch the power to the lamps thereby reducing the effective voltage thereto while providing sufficient light output to be observed. The modulator may be bypassed by a second signal line connected to the vehicle alternator to provide a continuous signal to the transistor gate, thereby providing full power to the lamps when the engine is running.

Abstract: The electrical system of a vehicle includes a primary voltage source for starting and operating the engine of the vehicle and an auxiliary voltage source for operating the electrical accessories of the vehicle, particularly when the engine is not operating, and a voltage differential monitor circuit for warning the vehicle operator of the existence of a low voltage condition of the auxiliary battery, such as resulting from an auxiliary battery charging system failure which could result in the inability of an electrical accessory to operate even when the engine is operating.