OK, my curiosity was piqued, so I downloaded the '84 FSM and did some looking myself and I came across the description of the rear heater, which has a single push button switch which combines heater fan switch and warm water flow control operation. The manual describes it as ON-OFF operation. The only illustration I could find was on page 24-35 of the manual.

Is it possible this might be your mystery switch? After all, a system that has a secret box and secret box packing ought to have a mystery switch, right? <img src="/forums/images/graemlins/wink.gif" alt="" />

Eric W.

'89 Dodge Raider -- 3.0L V6, MT, SWB