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Discussion Starter #1
I'm starting to find this electrical business very interesting, but I have a few more questions to throw out there. My driver's brake light has stopped working under normal conditions. I replaced the bulb and the tailight comes on when I hit my lights, but I don't get anything for a brake light. The only way I can make the brake light work is to turn on my right hand turn signal--then the brake light on the left side will work. Does this mean the problem is in the turn signal or at least the wiring near the steering column?

In trying to figure out what was wrong with my brake light I also found some wiring that seemed odd to me, and I was wondering if someone might know what possessed a PO to do this. There was a wire spliced (I use the term loosely /forums/images/icons/tongue.gif) from my headlight dimmer switch (red wire w/ yellow stripe) to the black lead on my driver's tailight. I thought it might be causing the problem I mentioned above, but removing the wire entirely has not affected either the problem or the operation of my dimmer switch. Was someone trying to make the tailights dim and brighten?
 

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As an electrician, I think you have a bad ground. Many bulbs have 2 filiments in them tied together with a common point (ground). When you have a broken or poor ground connection at a bulb, it won't light. But when you make a connection to the other filiment in that bulb, such as a blinker, it tries to find an alternate route to ground. This means it'll try to find a ground in a bulb some place else in the car connected to that circuit. Hence funny things happening.

Always look for the simple common problems first. Check for corrosion in sockets, end of bulbs ect. I gaurentee you, if you do this to all you sockets, you'll most likely finf the problem. Also, go to Home depot, Lowes, ect and buy some Nalox from the electrical department to use on the bulb connections. Nalox is an anti oxident compound that's used on aluminum wire. the stuff works great. Another favorite of mine is antisieze compound for bolts, this works well too. I use it on my battery connections.
 

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The brake lights and turn signals all run through the turn signal switch. That is probably the best place to start looking.

Does the bright side of the bulb ever work on the right side? You said the left works only when the right signal is on, which sounds like the turn signal switch to me.

As for the "fix" on the dimmer... it sounds like the PO was trying to get power to the rear lights. The red/ylo wire is the live wire for the headlights. Running it to the black wire, which is ground, is particularly brain-dead. Do your tail lights work now that you have removed this "fix"?
 

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Discussion Starter #4
The bulb on the right side works just fine, no strange behavior there. Removing the 'fix' didn't seem to affect anything. There are a few other strange things back by the left tail light though. Where the wiring harness runs from the front of the car, and just before it splits for the lights, someone cut the black wire (assuming ground?) just before it split into two wires (ground for each of tailights?), and then apparently changed their mind and just kind of looped them back together again and taped them up with black cloth tape. I suppose this could be part of a ground issue, so I will be soldering this wire back together. They also shaved half of the isulation off of the two wires that run to the back of the tailight bulb. One is green, and they didn't do anything with it, just taped it back up again to cover the bare wire, and the other is the black ground that they had connected to the live wire for the headlights. And this doesn't even touch whatever they did to totally disconnect the back up lights--I haven't delved very far into that issue as of yet.

I suppose I should repair that wire, then pull the steering wheel and take another look under there. I did notice that at some point two wires had been connected to the large blue and yellow wires that come down from the steering column to join the dash harness. The wires had been cut, but the connectors were left in place--don't suppose this could be part of the problem?
 

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At this point I would strongly suggest you aquire a good set of schematics. I got the set I use from Mustangs Plus and am quite happy with it.

From my '66 diagram it would appear that the blue/yellow wire is the horn. Does your horn work?
 

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Discussion Starter #7
I fully agree with you on the schematics--now that I've jumped into this, I definately need to pick some up.

As for the horn...well..it has worked..maybe three times. Very weakly. I guess I was thinking it might be the contact points under the steering wheel, but I suppose it could be the wires too...

Although looking at the online schematics tjbatzli pointed out, I can definately say that the wires going to my backup light switch have been cut. Not even sure if I have a switch anymore--but then I've never seen one so I probably haven't known what to look for.

By the way, thanks all for the advice. /forums/images/icons/smile.gif I've got alot of things to take a look at now.
 
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