found this thing under the dash, not hooked up. was wondering if had anything to do with a datsun-factory A/C system.

Can't really get a prospective of where that is under the dash but the two wires appear to be the ones that connect to the switch that controls the dealer installed AC that many of them had back then.

interesting as mine has the dealer A/C knob below the dash, but isn't hooked to it. the A/C system works, yet needs a charge by viewing through collectors' the site glass. thanks.

Site glass doesn't always tell the story depending on what refrigerant is in the system. Does it get cold? Those wires plug into the back of the switch and turn the compressor on and off depending on the position of the knob so I don't see how the system could be working without it. The switch should also have a copper thermocoupling that senses the evaporator temperature and cycles the compressor on and off to keep the evap. from freezing up.

it does work. i have two leads going to the knob. one is a fused line from the fuse box. the other is switched power to the compressor (blue line). the copper 1/16" tube goes into the evaporator housing somewhere...i just got the car a few weeks ago. the only time i tried it was in october when we had a warm day. the discharge from the compressor was cold compared to other body metal/parts. i ran it today to peek at the site glass. i did check the FSM re: bubbles in there, etc. i'll get it serviced in the spring.

Looks like a part that should be for Tach or dimmer ect. I just seen that on my car when I had the dash out and it is not for the AC.