kbavette

I have been on and off working on a 1969 vette.Now almost complete not frame off so no new wire harness.I put in a new headlight switch a couple of years back now have interior back in car and blows fuse .It blows the taillight fuse also.when turn counter clock wise to far left works and gets hot signal per test light.Then when turn to right as dimming blows fuse for instrument and also tail lights.So pulled left hand dash lower pad to verify no wires touching anything ,popped out or binding all is well there.I was wondering was there a way to test the headlight switch the blinkers work fine .Sorry so long just at witts end with this problem .......

Kilroy1024

Let me see if I understand this: If the headlight switch is in the middle everything works fine? But turned to either end it blows a fuse?

Check and see if your instrument lamps are dimming correctly.

The headlight switch is a variable resistor which makes full contact when you get to one end. If you had an instrument panel lamp wire shorted to ground, everything would be fine with the headlight switch in the middle. The resistive part would limit the current. When turned to full on, the dead short would blow the fuse.

The lamps are very dim, and if your working in a lit garage, you may not have noticed they weren't coming on.

kbavette

As soon as cut lights on fuse blows for instrument cluster.I did cut shop lights out to verify if working or not.. thanks kristian

Kilroy1024

So it blows the fuse when you turn it to certain positions?
Or immediately as soon as you turn on certain lights?
We're not there. It would help if you could reword it to be clearer as to which switch positions blow which fuse.

There are also dash panel lamps that are down in the center console by the shifter. The wire for the lamp that lights up the P R D 1 2 indicator can be worn if it rubs up against the shift mechanism.

kbavette

Now when i put a fuse in and turn on the headlights it blows immediantly .I did remove the left hand dash pad and now not blowing the tail light fuse but still no dash,radio,or ac control lights.Headlights and taillights work fine .I may have to hook up my old headlight switch and see if it may be the switch or is their a way to test the hadlight switch? thanks for any help..

Kilroy1024

There's a way to test everything...

Your headlights and tail lights are working, but you have no dash lamps.

Are you sure the fuse is blowing when you turn the switch full clockwise? This is supposed to be the dimmest lamp position and the fuse probably wouldn't blow even if the lamp circuit was shorted to ground. (Gray wire)
If this is the case, then I would suspect that the switch is shorted internally. Test it by removing the switch from the dash and operating it when its not attached to the chassis. - have it floating in mid air, not touching anything. Take a 12V test lamp and connect it between the switch housing and the chassis. Does it light up? If so, then the ouside of the switch housing is 'live' and it shouldn't be.


If the lamp circuit is shorted to ground, you should be able to test it as follows:
Turn the headlight switch full clockwise to dim the dash lights to off.
It should not blow the fuse now even if the dash lamps are shorted.

Pull headlight switch to first position, the tail lights and running lights should come on. Any fuse blows?

Pull headlight switch to second position. Head lights should come on.
Any fuse blows?

Start turning the dash lights counter clockwise 1/4 turn. You should see them start to come on. If they do come on, then that circuit probably isn't shorted. If they don't, and turning it full CCW blows the fuse, then the lamp circuit is touching ground someplace.

Kilroy1024

There's also a coil of wire at the front of the headlight switch that can fall out. If it does, it looks like a loose wire that is only connected at one end. This wire is the dash lamp dimming resistor. Its a resistive wire.
If its hanging out, it could be touching chassis. Its live when the headlight switch is pulled.