Restoring - General discussions that span across many different groups of years and models > Misc Items
Dash lights coming on when pressing brake pedal
midlife:
--- Quote from: Chris on October 04, 2017, 08:49:47 PM ---I checked for loose wires and did not find any, car was blowing the 15 amp fuse about every 4 minutes of run time (and when the headlight switch is on). I removed the wires from the brake master cylinder switch under the hood, drove the car for about 30 min and the fuse did not blow, brake lights and dash lights stayed on.
Not sure what this means though.
--- End quote ---
I don't either. If you disconnected the wires at the master cylinder, then the brake switch is now disabled, and you should have no brake lights. When you drove the car, was the headlight switch on? If so, that would at least explain the dash lamps. If headlight switch is off, there's something very screwy going on, and the headlight switch would be my focal point, as that is the source of both brake light power and dash lamps. The brake lights, though, have to go through the brake switch to be powered up. I wonder if by disconnecting the switch from the master cylinder, it defaults to making the connection. I've never seen a 64.5 brake switch.
Disconnect the headlight switch plug and see what you get. If OK, reconnect the master cylinder switch and see what you get. Process of elimination....
Chris:
Yes, I had the headlights on. With the break light switch disconnected, the headlights, dash lights, and tail lights all work but I have no break lights. I don't know why having the break lights disconnected keeps the fuse from blowing...is it because adding it is just too much amps for the headlight switch?
I can try the other steps you mentioned tomorrow.
Chris:
Just to clarify, with the break light switch disvonnected, all else operated fine (headlights, tail lights, dash lights) and the 15 amp fuse did not blow. The test was done with the headlights turned on. This is how I could see if the dash lights were staying on and the fuse remaining ok. When everything is connected (to include break light switch) and the headlight switch is on, after a short time the 15 amp fuse blows taking out the dash lights, tail lights, and break lights. Only the headlights remain on. This only happens at night when I'm running the car with the headlights on.
midlife:
Aha! I suspect the problem is a pinched wire or a shorted something or another at the rear tail lights. So try this: connect everything up, and disconnect the two rear light sockets. Does that allow everything to work (obviously not the brake lights or running lights at the rear) without blowing the fuse? If so, then connect the sockets and remove the bulbs. Does that work without blowing the fuse?
If so, examine the rear tail wiring very carefully; I'll bet something is amiss back there. Check carefully the grounds.
So why do the dash lights come on when the brakes are pressed? The lights are seeking a ground path, and the path they find are the dash lamp circuitry through the headlight switch.
Chris:
I reconnected the break (BRAKE)lights at the master cylinder under the hood and disconnected the bullet connecters in the trunk where they connect to the pig tails for the tail lights. I then drove around for 5min or so and the 15amp fuse did not blow. I then reconnected the bullet connectors at the tail lights but removed the light bulbs. I drove around for another 5min and the fuse did not blow. I'm about to put the bulbs back in and leave everything connected, drive for 5min and see what happens...want to see if fuse blows, need to make sure I was driving long enough.
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