1968 Electrical problem

[Ricky Knapik]

So I had a little problem show up Saturday night. I thought I'd post it here before the search begins. I'm sitting at a traffic light at night with the lights on and brake pedal pressed. My dash lights begin to flash. Thinking it's because I'm at ideal and maybe the alternator is not turning fast enough, I take my foot off the brake and rev it a little. (4 speed) The lights come on. My foot back on the brake, lights flickering again. I go about my evening cruise and head home. Now I start checking a little. Idling with the lights on, dash light are on and working properly. Put a stick on the brake pedal and everything seems fine. Then about 45 seconds go by and the lights start their dance. On, off! But being outside the car, I realize the brake lights, license plate light, and the front side markers are all doing the dance. Not the headlights. Hmmm! Release the brake pedal, everything is fine. Turn the head lights off, press the brake, 30-45 seconds later the brake lights are doing the dance. So it certainly is being triggered by the brake switch. I haven't even looked at a wire diagram, but seem odd for the brakes to feed back to the cluster. Any help would be appreciated!

 

[CougarCJ]

I would surmise that it is the added load of the 6 brake light bulbs being lit. Additionally, the turn signal switches are not near strong enough to carry the load. Common problem on the Cougars.
Changing to Plasma LED tail light bulbs, and electronic turn signal flashers is one solution.

 

[390gtmustang]

So I had a little problem show up Saturday night. I thought I'd post it here before the search begins. I'm sitting at a traffic light at night with the lights on and brake pedal pressed. My dash lights begin to flash. Thinking it's because I'm at ideal and maybe the alternator is not turning fast enough, I take my foot off the brake and rev it a little. (4 speed) The lights come on. My foot back on the brake, lights flickering again. I go about my evening cruise and head home. Now I start checking a little. Idling with the lights on, dash light are on and working properly. Put a stick on the brake pedal and everything seems fine. Then about 45 seconds go by and the lights start their dance. On, off! But being outside the car, I realize the brake lights, license plate light, and the front side markers are all doing the dance. Not the headlights. Hmmm! Release the brake pedal, everything is fine. Turn the head lights off, press the brake, 30-45 seconds later the brake lights are doing the dance. So it certainly is being triggered by the brake switch. I haven't even looked at a wire diagram, but seem odd for the brakes to feed back to the cluster. Any help would be appreciated!

I agree with cougarcj this happened to me on my HCS and all I did was replaced my tail lights bulb with led and it fixed it.

 

[franklinair]

+1 on the plasma LED bulbs. They draw far less current and are BRIGHT. You'll also have to replace the Flashers with Solid State types. (The original type Flashers won't function with the lower current draw.)
If you do have to replace the T/S Switch, the Scott Drake repro is the only one available that I know of ($84+/-) and the quality is questionable IMHO. If you need the tool to extract the pins from the connector, Radio Shack has them. ($10+/-)

Neil

 

[Ricky Knapik]

Thanks all! I did find a thread from about 6 years ago that Neil was involved with as well as many others regarding this topic. It was a lot of information to read. I've been super busy with work and chasing my boy playing travel ball so haven't had much time to check it out. What I did do is run it until the problem showed up. About 30 minutes at idle with the head lights and brake lights on. Once it started happening, it was pretty consistent. Since the left taillight plug has easy access, I reached in and unplugged the light and the problem stopped. Plugged it back in, and the problem reoccurred. So I'm confident LED's will correct the problem. In looking at LED bulbs at the local parts store as well as online, there are many styles to choose from. So what's everyone using? I want it to look as normal as possible!
Thanks everyone!
Ricky

 

[franklinair]

The Plasma LED's I used from WCCC P/N 10043 work well and are bright.
Regardless of who's LED's you use, you'll have to change the Flasher (both the T/S & Emerg) due to the lower current draw.

Neil

 

[Ricky Knapik]

Thanks Neil!

 

[Ricky Knapik]

UPDATE! So I finally had the time to do some work. I did a lot of research and talked to a few people that know a lot more than me. The obvious is clear, the tail/brake light system was not made to run 6 bulbs. The extra load is hard on the components involved, specifically on the turn signal switch. There have been many threads on this forum over the years on this topic, and they were all very helpful. The findings on my car turned out to be fairly easy. The ground wires to the taillight housings were lose. Not a great design! I took the taillights completely apart, cleaned the holes in the housings that the sockets fit in, cleaned the sockets themselves, and reassembled. When inspecting the sockets, I found 1 collapsed spring that needed repaired. I was able to find a spring that would work, and was able to roll it on. Worked perfectly. I decided to drill a small hole into one of the ribs of the housings for a secure ground. Someone had put a picture of that on another forum and it looked like a good solution. Then to finish it all off, 6 new red plasma LED bulbs. Those suckers are bright! I was told by many that I likely would still find a bad turn signal switch once I had the taillights fixed. So far I'm lucky and everything seems fine. I was also told that I would have to change the flasher because the LED's would not draw enough to make it flash. Not the case so far. I'm fairly certain the flasher is not original, so maybe I'm lucky that the flasher that's in it is doing the trick. So that's my success story. Bad grounds on the taillights and upgrade to LED's!

 

[robert campbell]

If you do not change the front bulbs, in my experience the two front bulbs will draw enough to make the stock flasher work.

Good call on the grounds. I actually soldered a ground wire to each receptacle, grouped, and ran a single wire into the trunk area. Then grounded it in the back panel inside the trunk for the latch mechanism.

Good grounds are the single most important aspect of a car. And most often it is a poor ground causing a ton of misery!

Rob

 

[Ricky Knapik]

Rob, I was thinking that between the indicators in the hood and the front sides I'd be ok. But most have had to change the flasher. I considered your path, but I tried this 1st. Fingers crossed.