I am trying to work out what the 3 push / pull cables on this control actually do.
One adjusts the demister / floor heatering position, what do the other two do?
One may turn the water control valve off, the other one I cannot find a use for

 

Probably opens up an outside vent as the engine heat tends to warm up the floor with no air-conditioning.

 

I will look for that, thanks

 

Yeah, back then it was commonplace as lots of vehicles didn't have air-conditioning, like they do now. Used to have kick-plates on the OTR cab-over-engines trucks back
then, but they would have looked real odd on a pickup. Even the Chevy the 50-60 series medium-duty trucks didn't have kick-plates back then.

 

What are you actually calling a 'kick plate'

 

They were small door inlets to keep the heat down, at the bottom of the door, so you kicked them open, particularly in the old flat-nosed C-O-E trucks when the engine was right next to the driver with a cover over it. Lots of rigs didn't have A/C (or power steering) back then, so you'd see drivers with one or two fans on the dash too. Lots of us have hearing loss in our left ears as the wind-noise with the windows down, took its toll over time. That and the "screaming Jimmy (loud GMC two-stroke diesel motors) didn't help either. Here is a photo of the kick panel or door, that the driver had chromed-up on this old Freightliner.