Abstract: A heating and air-conditioning system has an auxiliary engine for heating and cooling of a vehicle while the primary engine of the vehicle is not operating. The vehicle has a sleeper compartment with a sleeper compartment air conditioning unit powered by the main engine. An auxiliary air conditioning system located exterior of the sleeper compartment is powered by the auxiliary engine. An auxiliary supply duct extends into the sleeper compartment and joins the duct of the sleeper compartment air conditioning unit. A valve operated by air pressure blocks air flow from the sleeper compartment air conditioning unit into the auxiliary duct while in the main position. In the auxiliary position, the valve blocks air flow from the auxiliary duct into the sleeper compartment air conditioning unit.

Abstract: A collapsible step assembly has upper and lower steps, and a housing which mounts below the door of a vehicle. The steps and housing are interconnected by pivotally mounted linkages. A pivot rod extends transversely through the housing with a linkage fastened to each end. A link arm is connected to the rod with a universal ball joint. The link arm is swivelly mounted to a drive gear with teeth which extend circumferentially along an arcuate edge portion. The drive gear is pivotally mounted to the housing and engages a drive gear extending from a motor. The drive gear rotates the pivot rod and, hence, the steps between retracted and extended positions. A flat outer edge of the drive gear abuts a mechanical stop in the extended position. When the user steps on the steps while they are extended, the stop will resist countertorque on the pivot rod from being applied through the gears to the motor.