Delica Canada | Mitsubishi Van Club

HI ALL
I'm currently replacing my thermostat...and changing out the sensors around the Thermostat....I have been consulting my Service Manual...and they note the three sensors just to the right of the distributor (in the picture below)...but they don't specify the function of the fourth with ??????????? Any ideas? Would anyone here be interested starting up a Google groups or FB page for our vans, engines, etc? There is zero activity in these forums...and for someone new to these vans like myself..it would be very helpful to have a bit more pulse and realtime troubleshooting possibilities. Anyone? Anyone?
Thanks!

~A

I'm trying to remember back to when I had my vanwagon. I'm certain one switch locked out overdrive until the engine was up to a certain temperature. One locked out A/C clutch until the engine was a certain temperature. One was for the ecu to reference, and the last was the sender for the gauge. I don't remember which of them did all of these, but a wiring diagram might be helpful.