1968 Electrical problem when I press brakes, lights go off & on

[Batgirl89]

I dont know what it does during the day, but at night, with the lights on; when Im stopped with my foot on the brake pedal, the lights go on and off. The dash, front side markers, tail and brake lights.

The emergency flashers do not work when I push the button in, but if I put my foot on the brake pedal with the button pushed in, both blinkers and the tail lights go on (with the brake pedal pressed)

 

[Ruppstang]

Sounds like a bad turn signal switch. A very common problem with our cars. Marty

 

[franklinair]

Several possibilities. FIRST: Disconnect & clean both battery connectors & battery posts (positive & negative).

Neil

 

[robert campbell]

+ one. I have replaced mine twice over the years. Rvrtrash (Steve Wick) did some extensive research on this malady. Seems the original turn signal switches may have been from a Thunderbird and designed to hold 3 bulbs on each taillight. The replacements do not last as long. One thing to consider after the fix is LED tailight bulbs. They draw less current and the switch should last longer.

I will see If I can dig up the replacement proceedure we posted a few years back. It involves removing the steering wheel and diving under the dash! My least favorite thing is diving under the dash!! Anymore I remove the driver bucket seat for this crap!!

Rob

 

[robert campbell]

link to LED bulbs

http://californiaspecial.com/forums/showthread.php?t=7508&highlight=turn+signal+switch

 

[franklinair]

First check for power & ground (battery connections). Dash lights, side marker lights, tail lights do not go through thr Turn Signal switch.
At night, assuming headlights are on, at idle speed, foot on the brake: engine is at idle. This is the scenario when alternator/voltage regulator output is lowest. Any resistance built up in the battery connections can cause the symptoms you described.

Neil

 

[Batgirl89]

Neil, Ill clean and tighten it all tomorrow, I hope that works! I was hoping for an easy fix, not the turn signal wiring.....

thank you for all the help on this my GT/CS buddies!

 

[CougarCJ]

The Ford MPC shows that the replacement part for a 1968 Mustang with fixed steering column, is in fact part number C8SZ-13341-A.

Same as 1968 Thunderbird and 1968 Cougar.

*Note - Tilt swing steering columns used a different wiring harness.

 

[rvrtrash]

It actually sounds like you have two problems, the turn signal switch and the headlight switch. When the dash lights go out, do the headlights go out as well, do they flicker, or is there no change. I do agree on checking batt connections first. It's easy and doesn't cost anything, but it sounds like you have more in store in the future.

Steve

 

[CougarCJ]

If you have Halogen headlamps you will likely have problems with headlight switches. Too much draw.

 

[Batgirl89]

It actually sounds like you have two problems, the turn signal switch and the headlight switch. When the dash lights go out, do the headlights go out as well, do they flicker, or is there no change. I do agree on checking batt connections first. It's easy and doesn't cost anything, but it sounds like you have more in store in the future.

Steve

no problem with the headlights. the dash, front marker, tail/brake lights all go off and on together, sometimes fast or sometimes slow or they will be off awhile. when im moving no problems.

The headlights and dash lights do get bright with acceleration/reving. I did replace the voltage regulator in engine compartment yesterday, and notice more fluctuation with the light brightness.

 

[CougarCJ]

no problem with the headlights. the dash, front marker, tail/brake lights all go off and on together, sometimes fast or sometimes slow or they will be off awhile. when im moving no problems.

The headlights and dash lights do get bright with acceleration/reving. I did replace the voltage regulator in engine compartment yesterday, and notice more fluctuation with the light brightness.

That is an inherent problem with these Ford alternators. They do not charge when the engine is idling.

 

[franklinair]

My concern centered around the circumstances described: Just about a full electrical load on the 12V system, low RPM, and low alternator output that may be compounded by poor connection(s) at the battery. (Hope you installed a solid state voltage regulator.)
If the electrical system is OK, the problem may be twofold. Primarily the headlight switch, weak emerg. flasher, or the emerg flasher switch- which would require replacement of the turnsignal switch.
As a matter of curiosity, I'd like to know the voltage at the + battery post when the car is in the state initially described: all lights on, engine at idle.
Just take things one step at a time, process of elimination. Lots of help here.

Neil

 

[Ruppstang]

My concern centered around the circumstances described: Just about a full electrical load on the 12V system, low RPM, and low alternator output that may be compounded by poor connection(s) at the battery. (Hope you installed a solid state voltage regulator.)
If the electrical system is OK, the problem may be twofold. Primarily the headlight switch, weak emerg. flasher, or the emerg flasher switch- which would require replacement of the turnsignal switch.
As a matter of curiosity, I'd like to know the voltage at the + battery post when the car is in the state initially described: all lights on, engine at idle.
Just take things one step at a time, process of elimination. Lots of help here.

Neil

I agree with Neil, eliminate one thing at a time starting with the cheep and easy ones. Marty

 

[CougarCJ]

One other basic thing, that causes electrical issues is a missing engine block ground strap to the firewall.

 

[Batgirl89]

I dont know if the headlights are halogen. Sylvina xtravision sealed beam

Got the electronic voltage regulator (was fifty bucks! dang)

negative battery cable is a 4 ga. should it be a 2 ga? do I not have a good ground?? the cable goes from the battery post to the bolt on the water pump

I cannot find a "flasher" unit for the turn signals or emergency flashers under the dash

 

[Batgirl89]

One other basic thing, that causes electrical issues is a missing engine block ground strap to the firewall.

can someone post a pic for me so I can add one!

 

[Mosesatm]

Here is a photo of a ground strap. It attaches to the rear of the block.

 

[Mosesatm]

I dont know if the headlights are halogen. Sylvina xtravision sealed beam

Got the electronic voltage regulator (was fifty bucks! dang)

negative battery cable is a 4 ga. should it be a 2 ga? do I not have a good ground?? the cable goes from the battery post to the bolt on the water pump

I cannot find a "flasher" unit for the turn signals or emergency flashers under the dash

Those are halogen lights and they tend to overheat headlight switches.

If I remember correctly the turn signal flasher should be above the ignition switch towards the steering column, and the hazard flasher is way up high towards the center of the instrument cluster.
Here is a photo of where the hazard flasher should be if it's still in the clip.

 

[Batgirl89]

Arlie, thank you! im going to go dig around.