Re: 89 s-10 dash into 85 s-10
I got the newer dash panel guages to work with my original wiring harness!
here's what I did:
take the old panel and trace out all the connections on the printed circuit board, record which guage/light uses which connection (the connector plug has all the wires numbered on the plug)
trace the circuits out on the new instrument panel (numbered too)
record your findings
match up the apropriate wires/numbers to the guages/lights required (some items will double over, this is alright it will still work)
use jumper wires to test for the right connections before you change things around permanently (it's always too easy to mix up those printed circuits when tracing them out).
the connector plug comes apart so you can "reprogram" the plug to send the wires to the right connections. Oh yeah, use tape and number the wires before you take the plug apart, if you don't I guarantee you'll mix them up and then you're really screwed!
now my 85 has an 89 dash. Oh yeah, for those who wonder why I bothered, I changed it because I think the newer dash looks better than the 85 (changed door panels as well).
All I have to do now is hook up the headlight panel and the heater controls(piece of cake!). I had to find a heater control panel and cables out of a non air condioned truck.
So now I have the dash I want (even managed to hook up the side window defrost vents, the heater plenum box even has the outline where to cut for the air feed) and it all looks factory because there are no cut or spliced wires, just GM parts.
Don't get me wrong though, this wasn't easy, it took an entire sunday to work out the electrics and I'm still not done, but if you want to, it can be done.
Just a note:my truck is an 85 s-10 4x4 2.5l auto no air with the full guage package, the donor truck was an 89 s-15 jimmy 4x4 2.8l auto with air conditioning. your aplication may involve some additional problems besides the rewiring of the plugs.