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Driver Rear Brake Light Short


muwaha

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Hi All,

I have a 1991 Ford Ranger Supercab 3.0 V6.
I have an issue where the Driver's brake light won't engage when the pedal is pressed, but the passenger side does, as well as the headlight function and turn signal's work on it.
I have 2 questions on this that Google doesn't seem to be helpful with.

1. What is the voltage that suppose to be sent when the brake pedal is pressed?
2. Does anyone know what wire actually that is sent from the brake switch to the brake lights?

I have a Brown, Black, and light Green/orange on the driver side, and I know it's Brown, Black on the passenger side. The third wire is is orange something (unfortunately, I can't recall off the top of my head).
My Chilton Repair Manual is not helping me on the wiring diagram.
I ran tests on the brown wire and the light green/orange wire on the driver's side and getting 2 different voltage levels so I'm not sure which is suppose to be correct.
 


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ericbphoto

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RobbieD

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Lt green / orange should have +12 volts at the brake light socket with the brake pedal pressed, and if not you need to then check it coming out of the multifunction switch (turn light lever). I think it's 2 screws from the bottom, and the steering column shroud can be removed, exposing the switch and connector.

If you have +12 volts on the wire at the bulb socket, the contact inside (that touches the bulb) may be bent or broke.

Thanks, @ericbphoto, for posting the schematic link.
 

muwaha

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Thank you both for the help.
I may be blind (I don't have my glasses on at the moment), but I don't see the brown wire in that diagram.
I traced the light green/orange back to the firewall and saw it in the cab, but lost it in the bundle of wires under the dash lol.
So if I understand that diagram right, it goes into the connector on the steering column.
So I've used a T-Tap Splice connector (doesn't leave any expose wiring when the T-Tap is removed) running a small wire to a multimeter.

When I press on the brakes, the brown wire (unsure of where it goes) gets like 0.100 V when the brake pedal is pressed.
At least now I know that the light green/orange and orange/light blue are the actual lights for the brakes.

I don't see the wires that the diagram indicates for the turn signal..
 

RobbieD

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Brown is your parking lights, and those aren't shown on the stop / turn / hazard page. The tenth of volt you see on the brown may just be a cross feed, like through bulb filaments; I wouldn't be concerned with that at this point.

Meter set for DC, at the driver rear bulb socket, stick the meter black probe, from the back, in with the socket black wire. Parking lights on, meter red probe on the socket brown wire should show +12 volts. Press the brake, meter red probe to socket lt green / orange should show +12 volts.

If the lt green / orange is dead at the socket, expose the connector on back of the combination switch (pull the column shroud) and repeat testing the lt green / orange wire there, for +12 volts when the brake is pressed.

I don't see the wires that the diagram indicates for the turn signal.
The stop and the turn signal are the same animal. The combination switch works the one bulb filament for both functions. Pretty sneaky, huh?
 

muwaha

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So just an update.
I backed traced the wiring between the pigtails.
So there's a pigtail with the engine under the master brake booster.
I used a T-Splice into that and was only getting 0.005 V.

I figure I take the steering column off and all of a sudden the driver brake light starts working.
I have the steering column connector zip tie together because it was loose for the longest time (it was causing the truck to shut off shortly after starting, going dead down the road due to bumps disconnecting it, etc).

So if this green/orange wire does go to the steering column (I figure I check this before I digged into it).
 

muwaha

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I've been jiggling the wiring connector on the steering column and that seems to be fixing it every time.
Problem is that the brake light wire doesn't seem to come up to there so I'm assuming it converts to another wire color, but I can't find it on that diagram that @ericbphoto posted.

I was going to add a couple more sets of brake lights (one with a reverse light built in so I can hook those wires up) so I can get some magnetic ones and put on the sides of the truck for me to monitor it and adjust as needed until I can do more research.. Work has picked up hence my delayment on this.
 


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