Abstract: An improved control method variably activates an electric resistance heating element in a vehicle heating system so as to maximize the heating performance without overloading the vehicle generator or discharging the vehicle storage battery. A desired activation level for the heating element is determined based at least in part on the ability of the engine driven generator to develop electrical current, and when enabled, the heating element is activated based on the desired activation level. If a load condition for which the generator is unable to charge the storage battery is detected, the activation level is progressively reduced, and when the load condition is no longer detected, the activation level is progressively increased toward the desired level.

Abstract: An accurate and low cost sensing apparatus for a swash or wobble plate compressor that requires no modifications in compressor design or operation, and which provides a repeatable and accurate measure of compressor speed and stroke. The apparatus includes a sensor module and a stroke sensing circuit. The compressor has an outer housing formed of aluminum or other non-magnetic material, as is customary in automotive air conditioning systems. The sensor module includes a magnetic field responsive sensor such as a Hall Effect or magneto-resistive (MR) sensor, and is attached to the periphery of the housing in proximity to a reciprocating ferrous element such as a bushing shoe on the swash or wobble plate assembly. The sensor produces a quasi-sinusoidal output voltage signal having a frequency proportional to compressor speed, and the stroke sensing circuit determines the compressor stroke by band-pass filtering, amplifying, and peak detecting the signal.