I am a little confused about this 90 bird. The lights are throwing off the guages. When I put on the headlights with the interior light dimmer all the way down, the guages are reading fine. But as soon as I slide the dimmer to max, my voltage guage drops down 3 volts, oil pressure drops 20psi, and the temp guage also moves a bit. If i put the switch back to low, then everything returns back to normal instantly. The switch is dimming all the lights fine but it just messes with the guages. Anyone have any ideas?

 

ok problem is worst. now when set to max, all the guages shoot to their max except tach and speedo and the interior lights no longer come on. But when i turn it one more notch where it turns the dome light on, i get all interior lights + dome lights and the guages are still maxed. Dimmer switch maybe?

Fuses all good

I have also noticed that i no longer have sidemarker lights. Headlights, taillights, brakelights, and front parking lights all work though.

Also, i tried to jump the wires from the remote dimmer switch and i still have the exact same problem. The interior lights will only come on when the dash dimmer is set to the dome light mode.

 

i pulled the guage cluster out and took a look at the board and everything looks good. Couldn't find anything burnt or shorted. I also ordered a dimmer switch that should be in tomorrow to try. Anyway, anyone have a wiring diagram for the marker lights?