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Discussion Starter #1
repost no fix|: installed a new turn signal switch/cutoff connectors soldered wires.
i cant get both brake lights to work, only one at a time,both come on just not at the same time, it depends on where the t/s switch is.. i know alot of you say this is normal ,but with the key off or on , t/s in the center position only one brake light comes on. if i move the t/s switch in another direction the other one comes on BUT NEVER BOTH EVER,EVER,EVER, WHAT DID I DO WRONG,please im stumped..
 
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So you replaced the turn signal switch and now your brake lights no longer function properly? Humm... I'm not sure about that one. Do you have a wiring diagram? The only thing that I can think of is somehow you wired the two circuits together or blew the fuse for the brake lights. I don't think there is a separate fuse for that however. That is really strange. You may have to rewire the switch or try reinstalling the old one. I know this isn't much help. Hopefully someone else will have more insight into your problem.
 

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I can offer only this and I'm not sure if 71 is similar to 65 but:

The bulbs and grounds turn out to be the culprit most of the time. The taillight bulb (at least for 65) is combination brake light and turn signal. It is possible to incorrectly insert the bulb so that only one of the two nubs on the bulb makes contact, It will cause the problem you speak of.

If your turn signals work regardless of the brake lights, the problem will not be in the turn signal switch. If you don't have the diagrams get a set. They are necessary to troubleshoot these kinds of problems.

If you want to email the circuit diagram to me I'll take a look at it for you and see what I can come up with.

Good luck.

Frank
 

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Just out of curiousity, do the taillights work if you use the headlights and not the turn signals?

If so, I suspect a grounding problem. Did you put a piece of electrical tape behind the turn signal switch inside the steering wheel? Sometimes the back of the rivets touch the steering column (ground), and that usually burns out the turn signals within a 100 miles or so. Don't ask how I know that one!
 

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Since you can get both lamps to work, albeit not at the same time, this kinda eliminates wiring to the lamps, bulbs & sockets.

The turn signal switch is a delicate affair, and quite often the small wires attached to the moveable portion do not fully contact the stationary pins. Try depressing your brake and then push down on the t/s cam to see if both lights come on. You may simply need to bend the wires out from the cam slightly to make everything work.
 

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I agree 100%. Unfortunately, the repro turn signal switches are crap. I had the same problem, and spent 20 minutes installing the switch and another 2 hours FIXING the new switch so that the wires would contact the pins when they were suppossed to.

The turn signal switch is just another shining example of a part that would be SOOO simple to make right, but the manufacturer's don't care ... if it looks close, it's good enough for them. If it actually works, hey, a bonus!
 
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My recommendation is to buy an NOS Ford t/s switch. They pop up on ehay quite regular for under $40.
 

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I'll second (or third) the comments on repro turn signal switches. I've installed two so far and I've had to "adjust" them each time to get them working right out of the box. Now my second set is cancelling strange on right turns. Next time I'm paying for a FoMoCo switch. Since the brake lights are wired through the turn signal, it can produce the symptoms you describe.
 

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Discussion Starter #9
ok update mid i dont have the steering wheel on.maybe this will help
KEY OFF:
with the t/s switch set to the right turn position: when i hit the brakes the oil and fuel lights on the dash light up .in this position both brake lights work fine.
2. t/s in center position apply brakes , only passenger brake light works but both filaments light up.
3.t/s switch in Left turn position ,brakes applied,passenger brake light works both filaments again.
KEY ON:
1. BLINKER SET TO RIGHT TURN,PASSENGER BLINKS BUT BOTH FILAMENTS LIGHT UP.
2. blinker set to left turn,both taillights blink, like hazards are on(by the way hazards arent hooked up)
LIGHTS ON /KEY ON:
1.BOTH RUNNING LIGHTS IN REAR WORK,BLINKER SET TO TURN RIGHT,PASSENGER BLINKER BLINKS AND RUNNING LIGHT ON ,BOTH FILAMENTS USED .
2.BLINKER SET TO LEFT TURN ,INDICATOR LIGHT ON DASH ILLUMINATES BUT DOES NOT BLINK,ONLY RUNNING LIGHTS ON IN THE REAR.SINGLE FILAMENT,NO INDICATION OF BLINKER AT REAR.
3.WITH LIGHTS ON ONLY PASSENGER BRAKE LIGHT ILLUMINATES.
I HAVE REPLACED FLASHER,I HOPE THIS HELPS SOMEBODY,.... THANKS IN ADVANCE ,SORRY ABOUT THE CAPS I DONT KNOW WHEN THAT HAPPENED.....
 

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Excellent diagnostic clues.

I'd check the ground on the driver's side (front and rear!). Use a multimeter to ensure you're getting 12V to both for brake light and turn signals by disconnecting the socket and probing the contacts there. Then set the multimeter to resistance (ohms) and measure the resistance through each filament on the rear: should see 2-6 ohms.

My guess is that there is a bad ground, or bad contacts in the bulb socket. Bend the contact tabs towards the bulb and ensure they do not contact one another. These are the tabs that contact the bulb "[censored]" at the base of the socket.

The problem is definitely in the driver's side.
 

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Discussion Starter #11
hey midlife,i messed with the sockets on the back and i think we are getting closer, i moved the prongs a bit and tried all the flavors, lights on ,key on ,blinkers ,brakes and everything worked, but my brakes still seem to act screwy with the turn signal but not as bad,could need some adjustment or new t/s, i messed with the prong on pass side and now i dont have a brake light on the passenger side but i did that.. any way on the right track.
 

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Definite grounding issue.
Two things you need to solve this problem. 1. Wiring diagram.
2. VOM (volt ohm meter)
Make some resistance measurements from the tail light housing to a good chassis ground (frame rail, for example). Additionally, you also shoudl check out the grounding scheme for the front turn signal bulbs as well as the ground wire to the dashboard.
I would also start out with just checking the tail light circuit, then the brake light circuit and finally the turn signal circuit.

Good luck.
 

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Discussion Starter #13
looks like the sockets will fix 98 % of the problem,but as far as the turn signal switch affecting my brakes which might be normal now ,i dont know because i bent the socket prongs and lost one of my tailight/brake lights and had to go to work. but ill see tonight..are the sockets themselves replaceable alone or do you have to buy the whole taillamp assembly. thnks.
 

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Lamp assembly includes the socket, metal housing an pigtails for the wiring. You are fortunate that you have a 1966 model, as the 65 tail light assemblies were hard wired into the wiring harness (no pigtail connectors)...
 

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Discussion Starter #15
ok found problem!, i squeezed the t/s switch while it was in turn position and everthing works fine,i guess the contacts arent contacting..how do you fix the t/s switch to replicate me squeezing it together?
 
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