I have a 1989 4Runner. My dash lights stay on at the same intensity even when rheostat is adjusted. I have tested the rheostat and it ohmed out correctly (infinity-7-0). Even when I remove the rheostat, the lights remain on at the same intensity. I am assuming the rheostat has been bypassed but I do not know how to troubleshoot the issue or where the problem could be. The RRunner is stock and have not added or rewired anything. Anyone had a similar issue or a fix?

 

Here's the schematic for the 90-95 4Runner. I don't imagine it changed much from 89. You can see the rheostat near the bottom center. I sketched in what I think the rheostat is doing.
You should be able to check the wiring and see if the indicated fuse (15A Taillight) affects the dash lights. If your wire colors don't match the drawing it may be more challenging!

Good luck

Jim



90-95 dash lights

 

Thanks for the diagram. I was able to track down the diagram for my year, see attached. Again, I have removed and tested the rheostat and it is to spec. The lights remain on when the rheostat is removed so it appears something is bypassing the rheostat. I have no clue.

 

Have you checked that the ground lead from the rheostat actually goes to ground? It won't do anything if it's not grounded.

 

Led lights?

 

Not LED, the have made no modifications to the interior lighting system.

 

If the dash lights remain on at all with the rheostat removed, that means the R-B wire (pin 2) in your diagram is grounded somewhere. (You can turn the lights off and check that with a test-light or multimeter, but you can trust me on this.) It could be as simple as a short in the rheostat socket (pin 1 to 2). Since R-B is grounded all the time, a multimeter will be little help finding the "bypass." Instead, you'll either have to carefully inspect the wiring, or go as far as (for instance) cutting the W-B wire from the rheostat (if the lights go off, that means the socket itself is shorted. So now you need a new socket, and you have to repair the wire you cut.)