Ford F150 rear right BRAKE light problem

1976 Ford F150 pickup truck is having rear right brake light problem. The rear right brake light does not come on during braking. it also
does not come on during hazard flasher use.
1. Rear, right and left RUNNING lights work fine. 2. Rear, right and left TURN signals work fine. 3. Rear LEFT brake light works fine 4. Rear RIGHT brake light does NOT work 5. Hazard lights work EXCEPT for RIGHT...which does NOT light up.
I have changed bulbs, flashers, and tested the socket and wiring up to the connector under the tailgate and the bulbs etc are fine. Since both directionals are working, and the directionals use the SAME filament as the brake, I know it is something else.
Any ideas? How to chase down this gremlin. Spent all day cutting/splicing/trying to islolate the problem to no avail.
Any ford techs on here can help?
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TOP POST
It could be a break in the wire going from the left side tail light to the right side. Under the bumber?
Alan
papadad wrote:

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Anyone have a wiring diagram to explain what the 4 wires from the front of the vehicle to the rear bumper do? I am guessing that one is brake, one is left turn, one is right turn, and one is reverse. am I on the right track? And also a wiring diagram from those 4 wires to the 2 brake lights (2 filaments each)? Is the TURN signal (blink on/off) on the same line as the BRAKE signal? Does my question even make sense?
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papadad wrote:

I've always wondered what the mechanism was on how the turn signal overrides the brake light signal.
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Alan wrote:

It's built into the turn signal switch. With the lever in the "neutral" position, both rear lights are connected to the output of the brake light switch. When you signal a lane change, one of the lights is disconnected from the brake light switch and connected to the output of the turn signal flasher.
nate
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Most common problem with brake or tail lights is a bad ground. The light assembly is grounded to the body, and road salt or other junk causes corrosion at the connection and ruins it.
Dan
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Thanks to those who replied.
1) there are no trailer wires 2) all grounds are good, re-done, new etc. So not a ground problem 3) flasher itself (both turn and hazard) are working normally so not the flasher 4) i actually re-wired (temporarily) the RIGHT lights to the LEFT lights (in parallel) and everything works...further confirming it's not something ike a light bulb or a bad ground at the bulb socket.
The above post gives me a real (not a guess) lead -- I now suspect the trouble is in the turn signal switch itself - with the lever in neutral, both rear lights SHOULD be connected to the output of the brake light switch. But one is not lighting...maybe the turn signal switch on the steering column is faulty. It would also explain why, when using either right or left TURN (when the switch is in turn mode, not neutral positiong) that the rear lights each blink properly, ie, the wiring and the bulb and the socket are all functioning NORMALLY...also, no fuses are blowing so there is not a short anywhere. Remembering that the Blink and Brake are on the SAME circuit. So...somehow the TURN position is working but the BRAKE position (right side) is NOT.
I bet a dozen donuts it's a faulty turn signal switch. This is the best thing to go on, thus far, i mean, logically this makes perfect sense and the reason why I found no probems in the rear-end wiring after hunting for 2 to 3 hours the other day. No problem to be found back there.... Any other thoughts?
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Yep - I bet the turn signal switch "Neutral" position is bad. Try dis-assembling, cleaning, or at least wiggle it around a bit.
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Your hazards and brakes should be on the same 'fuse' circuit I think. The turn signals have their own fuse. Same bulbs and wires going on back so that part is fine, but their power supplies are different... My bet is on the hazard switch...
Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Jan/06 http://www.imagestation.com/album/pictures.html?id !15147590 (More Off Road album links at bottom of the view page)
papadad wrote:

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From memory, The brown wire is running /park lights. The yellow is left turn/brake light. The green is right turn/brake. Purple is back-up lights. Same bulb filament is used for brake and turn signal. Make sure the bulb is an 1157 bulb, and is inserted correctly. Also make sure any trailer wiring that has been added on is connected correctly.
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Your common issue seems to be with the emergency flasher. I would be checking out that switch for a bad connection. The hazards and brake lights are on the same fuse likely so are on the same wiring circuit.
Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Jan/06 http://www.imagestation.com/album/pictures.html?id !15147590 (More Off Road album links at bottom of the view page)
papadad wrote:

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Replace the signal switch. And if you are connecting a trailer, make sure the trailer is not overloading the circuit.

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So, how do I get into the steering column to get to the turn signal switch. Tried to remove the steering wheel but can't get it unstuck.
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Get a very strong friend to pull hard..... <grin>
Actually:
Steering wheel puller, sold at most parts supply stores. Cheap ones are under 10 dollars, but may not work well on a really tight steering wheel. Good ones are about 40 dollars.
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"papadad" wrote:
How do I get into the steering column to get to the turn signal switch. Tried to remove the steering wheel but can't get it unstuck. ________________________________________________________
It usually takes a wheel puller tool to get a steering wheel off.
Sometimes the contacts in a turn signal switch are intermittent due to corrosion, dirt, or grease. Before removing the wheel, try spraying electronic parts cleaner (some people use WD-40) into the turn signal switch through the side of the steering column while repeatedly (20-40 times) exercising the turn signal lever through its range of motion.
Good luck.
Rodan.
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On Thursday, May 11, 2006 at 10:05:24 PM UTC-5, Rodan wrote:

i just fixed my problem. thwires at the connector were broken. the insulation was still ok, but the wire was not making contact. bypass the connector and test the filaments with a testlight.
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Did it really take you ten years to fix it? --scott
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Scott Dorsey wrote:

I was wondering the same thing.
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Paul in Houston TX wrote:

I've had some problems that took over a year to figure out, but never as long as this poor guy. Hope it stays fixed!
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