86 GMC Sierra Classic 2500 questions

[motornut]

do yourself a favour and get rid of those blue connecters
they cause lots of probs, basicly cutting wires,allows moisture/salt in
they prob used it to connect a trailer harness.
may have removed the plugs too.
the cluster dimmer is controlled by a coil of wire that can burn out in spots,
a rheostat,if the switch is out (of dash)you can usally see it,might see the burn marks too
thats why it can work off and on when twisting the nob
the od goes to 99,999 then 0,later years have another digit