Driver's Side Brake Light Power Source - Not 12V

[UKPR1]

I thought I'd brake this issue out and separate it from my overall wiring issues with the truck. When I first got the truck, the PO had done a hack job on the rear wiring, and cut the yellow/blk stripe wire to the driver's rear brake light and spliced it into the green wire which appears to power the passenger side rear brake light. Stupidly, I reset everything without first finding out why he did this. I found out that with the wiring back in it's normal configuration, the yellow wire is barely getting 10V to the driver's side brake light. Passenger side brake light is fine as are both tail lights. The drivers rear brake light wire at the connector in the engine compartment (Wire # 283) is also reporting back 10V. So the issue is even further upstream that that connector. Driver's side barely glows that you can't even see it with the lens on. All grounds have been checked and I even ran a wire straight from the negative terminal to the bulb and the same issue persisted. All wiring is intact and continuous from the connector in the engine bay to the brake light bulb. In looking where #283 goes to from that connector in the engine bay, it gets its power from the turn switch(?). So my questions are:

1. Am I looking at a bad turn switch? This is all pre start-up and I haven't even determined if the turn signals operate as yet.
2. Why would Ford give 2 separate power sources for the left and right brake lights? Is it a load on wiring issue?
3. If it's not a load on wiring issue, is the preferred way of taking care of this to splice into the green operational brake light wire (#282) as the PO had done, and take the yellow #283 out of the equation altogether?

Thanks in advance,

Geoff
1969 F100 Ranger LWB
E18XXXX VIN - Built Late 1968?

[cep62]

The rear bulbs are for the tail lights and the brake / turn signal.
Power goes from the brake light switch up to the turn signal switch , then it gets distributed where needed.
In the middle both brake lights work , one way or the other one is brake the other blinks.

It could be worn out or just dirty , I would try flushing it with electronic cleaner.
You'll have to pull the steering wheel.

[UKPR1]

Thanks for confirming that the turn switch may be suspect, CEP62. Wondering if the wheel is coming off anyway, if it's just as simple to replace it?

Thanks and Regards,

Geoff

[cep62]

I would clean it and see if it helps your problem.
If it helps but isn't 100%, then buy a new one.
If it doesn't help , you'll need more trouble shooting.

[UKPR1]

Turns out you were correct CEP. I started "exercising" the turn signal while applying the brakes and little by little, the brakes lights started cooperating. My ONLY issue now, is that the turn signals themselves don't work at all - fronts nor rears. Not even the dash lights blink. I can hear the flasher operating though, just no lights. If the brake lights is on when I indicate, that side brake light goes out and then comes back on again when I cancel the indicator. If the indicator arm is telling the flasher to flash but there are no lights, is it still a turn switch issue?

Thanks,

Geoff

[cep62]

Yeah it sounds like it's time for a new switch.

[UKPR1]

Turn switch in...all the lights are happy again (even the dash lights). Oil and Alt lights are a little too happy though. My next forum question...

Thanks for your help.

Geoff

[UKPR1]

Turn switch in...all the lights are happy again (even the dash lights). Oil and Alt lights are a little too happy though. My next forum question...

Thanks for your help.

Geoff