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Question on my 67 Mustang

J

jmolayal

Senior member
Hey Gang... Got a 67 Mustang here and I can't get these tail lights to work. Its killing me! Here's the deal... Neither light works. Pull the headlights on, and they work fine. All other lights are good. All fuses are good. No running lights or Brake lights on the rear....

Changed out the bulbs and the lights worked... Hit the brakes, and they got brighter. Awesome... 20 seconds later.. No more lights. Checked the bulbs and they are not burned out...

I've got a new brake pedal switch on order and it will be here Friday. Any other ideas in the mean time? Broken wire somewhere maybe? Any good way to find it if it is? Thanks for your help!

- Jaison
 
Well, the first step is to get a VOM, turn the headlights on (so the taillights are on as well) and see if you're actually getting 12V or so at the bulb holder itself. Then find the place the 2 taillight wires connect, and measure the resistance from there to the taillights. Assuming it's good, you probably have a loose/broken wire further upstream. Keep hunting, junction to junction.

Also: Did you check all your fuses immediately before AND after you had working tail lights for 20 seconds? Can you change the bulbs again and once again get working tail lights for a few seconds, or do they stay dark this time?

Good luck man...electrical problems are pretty much the least fun to diagnose.
 
Well the old Voltmeter says I am getting Zip to the holders. Not good. Also not getting anything to the contacts where the holders connect.

I was afraid I would have to trace the wires back. I'm wondering if it wouldn't be in my best interest to just get a new brake switch and run new wires the whole length.. Don't these things just follow the floor all the way to the trunk?
 
Originally posted by: jmolayal
Well the old Voltmeter says I am getting Zip to the holders. Not good. Also not getting anything to the contacts where the holders connect.

I was afraid I would have to trace the wires back. I'm wondering if it wouldn't be in my best interest to just get a new brake switch and run new wires the whole length.. Don't these things just follow the floor all the way to the trunk?
Click to expand...

The tail light wires are different than the brake wires, unfortunately. Now, since you know your brake wires are good, you could try running new wires just for the tail lights...but you'd have to find what portion of it is bad. Which means you have to find out at what point you DO get power to the tail lights. How good were they about color coding?
 
Originally posted by: jagec
Well, the first step is to get a VOM, turn the headlights on (so the taillights are on as well) and see if you're actually getting 12V or so at the bulb holder itself. Then find the place the 2 taillight wires connect, and measure the resistance from there to the taillights. Assuming it's good, you probably have a loose/broken wire further upstream. Keep hunting, junction to junction.

Also: Did you check all your fuses immediately before AND after you had working tail lights for 20 seconds? Can you change the bulbs again and once again get working tail lights for a few seconds, or do they stay dark this time?

Good luck man...electrical problems are pretty much the least fun to diagnose.
Click to expand...

Kirchhoff's Laws FTW
 
I haven't ever had issues with any of the lighting in mine, so don't have any words of wisdom to give you. I will see if I can locate my manual with wiring schematics.
 
Thanks for the help guys. I appreciate it. I think I'll disconnect the wires from the brake light switch tonight and check em...

I also thought I might try applying 12V from a spare battery directly to the contact point for the bulb holders. See if the bulbs light up.

Picked up another set of bulbs too. Planning on swapping those in to see if they light up. I'll keep you all posted.

- Jaison
 
Check your grounds as well. Use the volt meter to check from the center terminal to the frame to see if you have 12V. If you do, and you DON'T have 12V to the socket and the center terminal, then you don't have a good ground path to the sockets.
 
Got it fixed. Turns out it was the headlight switch, not the brake light one. My handy repair manual pointed out that this switch controls the horn, parking lights, and instrument lights, all of which were not kicking on. $28 later, I'm good to go.

Thanks for all the advice guys. I appreciate it!

- Jaison
 
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