Dash lights not working

[boeing747arowair]

Good afternoon I recently got a 71 coupe in which im having issues with my dash lights working.

Current Status:

Headlights work, new headlight switch.

The small dash illumination fuse 4A keeps blowing even after installing a new headlight switch.

I noticed yesterday while snooping around with my voltmeter is that with fuse removed, i have continuity between both terminals when the switch is off. Continuity disappears when switch is turned on.

I do have 12v at one terminal of the fuse, but fuse does blow.

I have yet to remove the dash cluster to investigate.

One more odd ball, the PO removed my door courtesy light switch from the drivers door. I have not yet replaced but wanted to put that out there just in case it has to do with anything.

thanks guys

 

[marks73]

So, where are the wires hitting on the disconnected switch?

 

[midlife]

There are lots of places for the dash lamp wiring to be nicked and sent to ground, which is why you get "continuity" when the fuse is pulled and the headlight switch is turned off.

Start by removing every bulb on the circuit (check socket for correct pin location...don't have the two pins touching!), and reapply the fuse and test the headlight switch. If the wires are pinched, the fuse will blow. If not, one of the bulb sockets is damaged. Start by turning off headlight switch, plug in bulbs one at a time. Once a bulb causes the fuse to blow, that bulb circuit will be the culprit.

Have plenty of fuses on hand...this make take some time.

 

[don29163]

don't forget, lots of lights dim with that switch....heater, radio, aftermarket gauges

check what wasn't factory first.

 

[RacerX]

A way to test the circuit without burning up a bunch of fuses is to get one of the 12V incandescent trouble light bulbs. looks like regular old household bulb, but runs on 12V. Put it in a trouble light and use alligator clips to connect it in series in place of the fuse. With power on the circuit, if the short still exists, the light will glow real bright instead of blowing the fuse.

When you find the short and remove it, the light will either go out or go very dim as it's then not the biggest resistor in the circuit.

 

[boeing747arowair]

Excellent guys i appreciate i will look into that. After reviewing the wiring diagrams, i want to check the illumination cable that goes to the radio, the PO installed a custom autosound. for some reason i have a feeling something might have happened there as the rest of the dash/car is unmolested will keep you posted

 

[boeing747arowair]

anyone else?

 

[RacerX]

112122]anyone else?

So you pulled all the bulbs from everywhere and it's still shorted?[/u]