I have a 1970 Cutlass and the dash lights (not the warning lights) are on all the time with or without the keys in the ignition. When I remove the 25amp CLK/LTR/CTSY fuse they go out, but from my understanding the cluster lights are supposed to be powered by the 4 amp INST/LPS fuse and not the 25 amp fuse. i have removed the headlamp switch and checked to ensure it is functioning properly and all appears to be good. Has anyone come across a similar issue or have any suggestions on where to start?

 

There are two circuits: (1) 4A INST/LPS (fused) circuit for the instrument lamps; and, (2) 25A CLK/LTS/CTSY (fused) circuit. As correctly represented in the CSM color wiring diagram the 25A circuit is comprised of all courtesy lamps (not instrument lamps) to include glove box lamp, cigar lighter, glove box lamp, trunk lid lamp, clock, map lamp(s)/map switch & dome lamp. Note there are certain locations which are suspect to ground faults e.g. door jam switches.

I suspect you have a ground fault since CLK/LTS/CTSY lamps illuminate with car off and key out of ignition (w/ fuse inserted). However, you didn't completely identify the "state" of each (all) device(s) w/in that circuit [e.g. clock, cigar lighter, trunk lid lamp, glove box lamp, map lamp(s)]. This ground short would be closing (completing) the circuit for each device located (wired) in the 25A CLK/LTS/CTSY (fused) circuit. With that said, I might suspect a grounded LH DOOR KEY BUZZER & DOOR LAMP JAM SWITCH. What is the status of the DOOR KEY BUZZER with & without the keys in the IGN SW when the car is OFF? Review the wiring diagram and evaluate ground(s) located in the 25A CLK/LTS/CTSY circuit.