Problem between A/C and non A/C car is (except compressor, evaporator, condenser etc..) under the dash ! - Non A/C car has a manual air duct / cowl doors which is actuates by a lever pedal. Heater housing is different. Also ducts and cowl door frame. In fact all the parts are different ... - A/C model 900 car has an hydraulic operated "recirculating/cowl door" actuated via the solenoïd (2 doors, one under the cowl grille and the other behind the plenum chamber / evaporator; the doors are linked so when one is closed the other is open). If the solenoïd doesn't work (or if you're in the "heat" toggle switch position) the cowl door remains open so you've always air coming from the cowl grille to the ducts, heated or non heated depending position of temp. lever. When you shutt off the engine it's the same thing. When you put A/C on, the solenoid is energised and oil acts on power piston which opens the recirculating door (and closed the cowl door). Interior air of the car passes through this door, cooled by the evaporator and is distributed through the air ducts. You could also add heated air if you push the temperature lever to "warmer". So Hugh, don't worry, you'll always have exterior air in your car: plug the line coming from the "T" to the solenoid. But if you want a working A/C, you must have a working power piston. and new lines.. -- Philippe COURANT (Pau, France) Imperial 57 Crown convertible Buick 58 Roadmaster sedan - American Car Club de France (ACCF) : http://www.accf.com - Chrysler Imperial France : http://www.ifrance.com/c-i-f - Cadillac " Standard of Excellence " : http://www.ifrance.com/accf-cad - SportsCars : http://www.ifrance.com/accf-sprtcar