I feel your pain i have the same problem right now it happens on my left side i changed the TS switch changed all the bulbs checked for grounding problem and i still got the same problem. when you find out what it is please let me know
chris

 

what model is the car and I will look at the schematics.

 

It's a 65 coupe. Thanks!

 

Must be the stang wiring gremlins. I have been fighting for months. At this point I have no front pass turn signal and no rear driver side brake or turn signal. Go figure all else works.

 

your brake lights go thru TS switch and i would guess thats where your problem is. other possibily is pins shorting out in TS/brake connector on steering column.to locate look for pin that could cause this from schematic. if you neead help in what pins to check PM me and i will take a shot at it.

 

Sounds similar to the problem I just narrowed down.
It sounds like its the front running lamp coming on, not the turn lamp.
Figure out which wire the current is coming through to that front lamp and trace it back.
According to my schematic the only connection I see between the brake switch and the front running lamps is the black w/yel wire which goes to your headlight switch .
The green w/red wire from your brake switch goes through the headlight switch also.
If I had to guess, I would suspect a bad headlight switch.
However, it is odd that both front lamps are not coming on unless the filament is bad or some other problem exsists on the other side. Do both front running lamps work?

 

My front running lights do not work when the head lights are turned on, also the green blinker light on the dash comes on when i step on the brake.

 

My running lights are not on with the headlights either.
Only with the headlight switch halfway out.
With the switch halfway out do both running lights work?

Check your grounds as others have suggested.
Start unplugging stuff one at a time and see if the problem
ever goes away. I would definately try unplugging the headlight switch and also the larger of the 2 plugs coming out of the steering column. Lets see if we can narrow down where the problem might be.

What side is the offending running lamp on?

 

Its on the drivers side. I'll go check running lights etc out now and report back

 

The black and yellow wire is disconnected about 6 inches from the lights so my parking lights are not even connected. Unplugged both rear lights and still get the same symptom. When I look under the dash there are some wires coming from the steering column that have been cut and twisted back together, at least one has an extra wire twisted with it, i think this may be my problem. I am obviously getting power back through the blinker circuit from the brake light circuit and it has to be shorting somewhere after the switch that causes the blinkers to blink.