Quote:
Originally Posted by pj67coll
If by blower switch you mean the large rotary switch between the two left/right side heater switches? I have one I bought new for my last 240D which I never installed.
What is the Off position for the A/C thumbwheel? I've never had one that works so I have no idea.
- Peter.
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The 240D climate control is real simple.
3 knobs and 2 levers and an A/C switch on the top panel (where the sunroof, rear dome, rear defroster, antenna switches are).
Left knob - turns on and off the the heated water for the left heat core.
Right knob - turns on and off the heated water for the right heat core.
Both of these are all mechanical, they connect to Bowden cables that pull on the valves on the firewall. 240D had dual zone heat, very fancy!
Center knob is a hybrid electrical/mechanical switch. Between 6 and 9 o'clock this operates the fresh air flap. Closed at 6, open by 9. At 9 the blower motor gets switched on with both resistor segments in line (low speed). At 10:30 one of the resistor segments is bypassed (medium speed) and at 12:00 the entire resistor is bypassed (high speed).
The levers change the air flow direction between defrost, panel vents, floor vents. Strictly mechanical.
The A/C knob is a potentiometer that works with a thermostat bulb in the evaporator. It alters the duty cycle of the compressor to regulate the cooling and prevent the evaporator from freezing up. The 1st gen 240Ds had a rotary knob (axis of rotation perpendicular to the panel) and the 2nd gen a thumbwheel. At one end of travel (the OFF position) the compressor is disabled. At the other end (MAX), a vacuum solenoid is actuated and this closes the recirculation door.