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post #1 of (permalink) Old 02-25-2002, 10:59 PM Thread Starter
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brake lights

while driving down the road, my dash lights and brake lights quit on me. when i got home and checked the fuse(it was blown) and replaced it. still no brake or dash lights. the odd thing is that when i hit the brake pedal, the turn signal indicator lights on the dash light up. anyone know what the heck s going on here and how to fix? thanks in advance


'79 CJ-5

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post #2 of (permalink) Old 02-25-2002, 11:52 PM
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Re: brake lights

This sounds like an all too frequent grounding issue. Your body to frame ground seems to have gone away. The power you send to the brake lights when applying the brake pedal is getting to the lights, but it can't get to a ground so the power searches for a route to take. Usually finding it's way to ground through another load , it is trying to go through the turn signal circuit as this and the brake lights use the same fillament in the bulb. That is why your dash turn signal indicators are glowing. Try a temporary fix by running a wire from the taillight bolts (where they come through the body) and running it to a "Known Clean ground". This should give you the answer you are looking for. Then it's just a matter of re-grounding the major systems to make it back to the - side of the battery.
Major systems being... Body/dash, engine, frame, grille(headlights/turn signals). It all has to have a clean route back to the battery to work properly. Good luck!


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post #3 of (permalink) Old 02-26-2002, 12:11 AM Thread Starter
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Re: brake lights

Thanks for the response. I guess i am gonna have to do some searching tomorrow.. i dont think there is a "good" ground anywhere on the jeep. Just to be clear, a loss of the ground can result in A) a blown fues, b) brake lights not working, and C) things that didnt work before(turnsignal indicators) to light up better than the christmas tree? my Voltmeter also jumped from 12 Vs (before blown fuse) to 14 after the fuse blew

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post #4 of (permalink) Old 02-26-2002, 07:57 AM
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Re: brake lights

Your absoloutly right on all accounts. A weak ground will blow a fuse, it adds more load to the circuit than the fuse can handle, a bad or open ground will cause the re-routing of power to find a ground through another source. Looks like you have some work ahaed.


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post #5 of (permalink) Old 02-27-2002, 11:35 AM Thread Starter
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Re: brake lights

after making sure the lights were grounded to a known ground, i checked the fuse, and did the tribal dance to the jeep gods, i had a buddy stand behind the jeep as i hit the brake pedal...and nothing happened. the TAIL lights now work, but still no brake lights.

i did the ground to known ground on the body, should i attempt to find a good frame ground?(i dont know if one exists)


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post #6 of (permalink) Old 02-27-2002, 11:50 AM
 
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Re: brake lights

The chances are pretty slim that a bad ground would blow a fuse on a lighting circuit (could happen on an inductive load, such as an electric motor), but anything's possible.
Don't over look the fact that you may in fact have two or more problems. (ie: bad ground AND soemthing else)
Do the turn signals work? If they do, but the break lights don't, it's either the brake light switch or the turn signal switch (or possibly both).
If neither the brake lights or the turn signals work, it'll take a little more troubleshooting to find the problem. You could still have a bad turn signal switch, but there could also be a wiring problem.
You may ask why I keep bringing up the turn signal switch, here's why it could be the problem:
On most American cars (that don't have amber lights in the back) the same bulb does the turn signal and brake lights. Something has to coordinate that. The brake pedal makes both lights come on, yet they are controlled individually for turn signal operation. However, if you turn on the blinker while the brakes are apply, it will still flash. How does this work? It's all done in the turn signal switch. When you turn on the left blinker, the left brake light get's disconnected. That switch also isolates the turn indicators on the dash so that they do not light with the brakes.

So, if either the blinkers or brake lights work, then you know the wiring is good (since they use the same wire) and you can start the troubleshooting with switches. If neither works, you'll need to varify that all the wiring is intact, but don't rule out bad switches.

Hope I made since and this helps you out [img]/wwwthreads_images/icons/smile.gif[/img]

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post #7 of (permalink) Old 02-27-2002, 11:54 AM
 
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Re: brake lights

I just read you're post again and realized that you're dash indicators light when you hit the brake. In that case, it's almost got to be a bad turn signal switch. I think I'd start by replacing it.
Do the turn signals work?

-Derek Schwab
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post #8 of (permalink) Old 02-27-2002, 11:55 AM Thread Starter
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Re: brake lights

well, the brake lights have NEVER worked since I've had the Jeep. i was actually planning on trying to fix THAT problem this weekend, so it looks like both brake lights and trun signals are getting fixed...

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post #9 of (permalink) Old 02-27-2002, 11:59 AM
 
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Re: brake lights

But you say the trun signal lights on the dash light when you hit the brake? That means your brake light switch is good. You probably just need a turn signal swith. It shouldn't be too hard to change, but if you have a locking wheel, you'll need a lock plate compressor to get to it.

-Derek Schwab
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post #10 of (permalink) Old 02-27-2002, 12:00 PM Thread Starter
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Re: brake lights

looks like a little project for the weekend. thanks for the help. let ya know how it goes

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