Page 54 - Demo

Page 54.Alvis Three Litre Shop Manual - T.A. 21 and T.C. 21HEATING & VENTILATING SYSTEMThe heating and ventilating system is designed to provide heated or unheated fresh air ventilation within the car and enables a constant interior air temperature to be maintained under all weather conditions.Fresh air is taken in through a duct situated behind the left-hand front wing and is fed into the car by an electrically driven centrifugal blower. Before entering the car the air has to pass through a hot water radiator in which it may, if desired, be heated by the engine coolant. The main air supply enters the body of the car through a controlled aperture in the bulkhead in the region of the front occupant%u2019s feet, and a controlled supply of air may also be directed on to the windscreen for demisting and defrosting.The quantity, distribution and temperature of the ventilating air can be accurately regulated by a quadrant type control which has two knobs marked %u2018AIR%u2019 and %u2019DEMISTER.%u2019 These knobs control the flow of hot water through the radiator, and also the valves which regulate the quantity of ventilating and demisting air. The blower is controlled by a separate switch adjacent to the control knobs.Each control knob has three positions, %u2018OFF,%u2019 %u2018 COLD%u2019 and %u2018HOT.%u2019 With both knobs in the %u2018OFF%u2019 position no air can pass into the car through the ventilating system.When the %u2018DEMISTER%u2019 control knob is moved to the %u2018COLD%u2019 position, the whole of the output of the blower is delivered unheated to the windscreen; intermediate positions of the control knob between %u2018COLD%u2019 and %u2018HOT%u2019 cause the air to be heated to the desired degree. Alternatively, if the %u2018AIR%u2019 control is operated in a similar manner and the %u2018DEMISTER%u2019 control retained in the %u2018OFF%u2019 position, then all the air will be delivered into the interior of the car at the desired temperature.In the case of both controls, the operating positions are the %u2018OFF%u2019 position or anywhere between the %u2018COLD%u2019 and %u2018HOT%u2019 positions; it is not intended that the control knobs should be set anywhere between the %u2018OFF%u2019 and %u2018COLD%u2019 positions.A large number of combinations of control positions are possible to obtain the desired temperature within the car whatever the prevailing external conditions may be. In moderately cold weather it will probably be found best to have hot air entering the interior of the car through the bulkhead and cold air for demisting the windscreen. Under conditions of extreme misting and icing it may be necessary to have all the heated air directed on to the windscreen. To get cool air, set demister to cold and air to off.Air conditioning controls.