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Another Electrical Question

zupanj

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I keep blowing fuses to the brake light/accessories circuit. I am about to go crazy with this. I put in a fuse and everything works for a little while and then, someone tells me I have no brake lights. When I check I find a blown fuse. I have looked at the brake light switch and it looks OK but I think it has to do with that switch. When I put in the master cylinder I had pulled the white wire off the switch accidently and seemed have moved the switch out of position during my ham-handed removal of the old master cylinder. I am going crazy with this. I have to be shorting somewhere but I can't imagine where. If I put in a new fuse, the glove box light, the dash courtesy light and the ignition switch light all work including the brake lights. Today I turned on the emergency flashers because that is wired in series and it also worked. When I tapped the brakes the fuse blew. I am wondering if anyone has run into something like this before?

Jack
 

69hemibeep

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zupanj said:
I keep blowing fuses to the brake light/accessories circuit. I am about to go crazy with this. I put in a fuse and everything works for a little while and then, someone tells me I have no brake lights. When I check I find a blown fuse. I have looked at the brake light switch and it looks OK but I think it has to do with that switch. When I put in the master cylinder I had pulled the white wire off the switch accidently and seemed have moved the switch out of position during my ham-handed removal of the old master cylinder. I am going crazy with this. I have to be shorting somewhere but I can't imagine where. If I put in a new fuse, the glove box light, the dash courtesy light and the ignition switch light all work including the brake lights. Today I turned on the emergency flashers because that is wired in series and it also worked. When I tapped the brakes the fuse blew. I am wondering if anyone has run into something like this before?

Jack
This could be in allot of places, its best you send it to me instead of driving yourself nuts :D I believe you can pull the flasher and still have brake lights. Do that and see if it still blows the fuse. Trying to narrow it down,I'm going to look at a diagram and see if it could be in the column
 

moparchris

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It sounds like you need to go out and buy a quality ohm meter or a multimeter. I have a ancient Fluke 88 and it is a life saver! What I have done in the past with this problem is disconnect the BLS (brake light switch) and hook up the the meter to the wire going to the BL harness. It should read a significant amount of ohms. If the brake light circuit has a short to ground then it will read close to zero. Then you must expose that wire and visually check the wire for damage to the insulation. When its a new problem on a car that has been together for a while its usually in the socket or where the wires have traveled over a sharp object. These problems take quite a bit of time and patience, but with the right equipment and a little knowledge you can totally conquer this. A shop manual will help you understand where the wires go and what they do. I hope I have shed some light on this and it helps you. Good luck.
 

69hemibeep

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Jack, looking at my diagram it could be allot of things. Like Chris said a meter would help. If not get a diagram and you can unplug harnesses, switches and such to hunt it down. Just a short list let alone wire and sockets.emergency switch and flasher, turn signal switch brake switch.
 

zupanj

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Thanks for the input. I have been looking at the wiring diagram which is in the reference section by the way. There is only one wire going from the fuse box to the brake light switch and a second wire from the switch to the emergency flasher so that seemed to limit the possibilities.

It turned out to be the switch itself. I kept coming back to the fact that everything worked fine until I changed the master cylinder, so it had to be something I did. The switch has a nylon leg with a small button on the end. I noticed the button was broken off the switch but figured that would only affect the adjustment. When I did a continuity check from the switch terminal to ground I got a reading (actually a buzzer on my voltmeter). That didn't seem right so I removed the switch and took a look. It turns out the nylon leg has a steel center and the steel was exposed when the button broke off. When the switch was energized it must have caused a dead short through the leg to the brake pedal, who would have guessed. Luckily I had a new switch and installed it and everything now works like it's supposed to.

Thanks again for your help. By the way Bob, don't you already have a hemi Roadrunner?
 

69hemibeep

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zupanj said:
Thanks for the input. I have been looking at the wiring diagram which is in the reference section by the way. There is only one wire going from the fuse box to the brake light switch and a second wire from the switch to the emergency flasher so that seemed to limit the possibilities.

It turned out to be the switch itself. I kept coming back to the fact that everything worked fine until I changed the master cylinder, so it had to be something I did. The switch has a nylon leg with a small button on the end. I noticed the button was broken off the switch but figured that would only affect the adjustment. When I did a continuity check from the switch terminal to ground I got a reading (actually a buzzer on my voltmeter). That didn't seem right so I removed the switch and took a look. It turns out the nylon leg has a steel center and the steel was exposed when the button broke off. When the switch was energized it must have caused a dead short through the leg to the brake pedal, who would have guessed. Luckily I had a new switch and installed it and everything now works like it's supposed to.

Thanks again for your help. By the way Bob, don't you already have a hemi Roadrunner?
Not in that color :D
 

Roadcuda

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69hemibeep said:
zupanj said:
Thanks for the input. I have been looking at the wiring diagram which is in the reference section by the way. There is only one wire going from the fuse box to the brake light switch and a second wire from the switch to the emergency flasher so that seemed to limit the possibilities.

It turned out to be the switch itself. I kept coming back to the fact that everything worked fine until I changed the master cylinder, so it had to be something I did. The switch has a nylon leg with a small button on the end. I noticed the button was broken off the switch but figured that would only affect the adjustment. When I did a continuity check from the switch terminal to ground I got a reading (actually a buzzer on my voltmeter). That didn't seem right so I removed the switch and took a look. It turns out the nylon leg has a steel center and the steel was exposed when the button broke off. When the switch was energized it must have caused a dead short through the leg to the brake pedal, who would have guessed. Luckily I had a new switch and installed it and everything now works like it's supposed to.

Thanks again for your help. By the way Bob, don't you already have a hemi Roadrunner?
Not in that color :D
And yours is bigger then his!!!! the hemi that is :pot:
 

zupanj

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And yours is bigger then his!!!! the hemi that is He!He! :jester: :jester: :jester:

I forgot to ask, does anyone have a part number for the dome light bulb, my was burned out.
 
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