need electrical diagram for brake lights desperately...have no brake lights

kburley · Jan 26, 2019

i have no brake lights to the tail lights or 3rd brake light

2005 b4000 4x4

so far:
replaced pedal switch
checked connections to multifunction switch
checked grounds on bulbs

i have tail lights and signals but no brake lights.

i am chasing the wiring trying to figure out what wires go where so i can troubleshoot grounds.

all fuses as far as i know have been checked. i have power through to the multifunction switch from the pedal switch. i am stuck trying to figure out what to check next.

if anyone can help via personal experience, knowledge or wiring diagrams i would be very grateful. i need to get to work on monday morning. thanks

RonD · Jan 26, 2019

Just one fuse powers the brake lights, #19 in cab fuse box 20amp

The cab brake light is powered directly from the pedal switch
The tail lights brake power runs thru the Multi-function switch(turn signal stalk)

2004 wiring below
Don't have a 2005 but do have a 2006 and its the same as 2004 UNLESS you have an STX model Ranger, then all 3 brake light bulbs are direct wired, multi-function switch is not used in that model for brake lights.

Cab brake light uses a different ground than tail lights, and if parking lights work the rear ground is OK.

Replace the 20amp fuse or TEST IT, do not look at it and think its OK

Brake pedal switch has two switches inside, multiple wires, its also used as a sensor, as well as for brake lights, brake light wires are 2, light green/red stripe wire IN from fuse #19, and light green wire OUT to brake lights

Long shot but maybe cab brake light bulb burned out a while back, and your problem is the multi-function switch, but shouldn't be because cab brake light also doesn't work.............lol, so some tail chasing if that bulb is burned out

adsm08 · Jan 27, 2019

I'm with Ron, check the fuse and the bulbs.

Many years ago I once spent an hour chasing my own tail trying to figure out a no brake light concern that was three burnt out bulbs. I assumed it couldn't be that easy and made it much harder.

This was the same week I watched a senior master diesel tech spent two hours diagnosing a "died on road, won't restart" concern on a Ranger that was out of gas. That man was a wizard with diesel engines, but if you handed him something that ran on gasoline he was lost.

kburley · Jan 27, 2019

i checked the bulbs and fuses. none were burnt out. i want to try a new multifunction switch but cant get one since nothing is open sundays. all other lights work so i know i have ground at the rear and i tested for ground on top and it was good too. im going to keep dovong into it today.
RON, that electrical diagram was very helpful. but i am wondering if my 3rd brake light runs through the multifunction switch and breaks off after. because it does seem highly unlikely in this case that all 3 lights would go bad. especially considering no bulbs are burnt out. i will keep you guys posted, and thanks for the input. my biggest issue so far is trying not to waste time diagnosing problems in a circuit that i do not understand (with no drawings).

Uncle Gump · Jan 27, 2019

Step one... make sure you have power at the brake switch and power out when you hit the brake... if good continue to step two. If you have power in but not out... replace the brake switch. If no power in... repair that circuit

Step two... at the multi function switch connector ensure you have switched brake light input power with the pedal pressed coming into the switch. if not... repair wire between switches. If so... check the two output circuits with the brake pedal pressed... should have power on both. if not... replace the switch.

Being that the turn signals work... it can't be the rear lamp circuits.

Edit... looking at the schematic... if correct for your vehicle... if the chmsl and rear brake lights are out... you said you checked all the bulbs (did you check the chmsl bulb and for brake input with a test light?)... the most likely cause would be the brake switch or power to it.

RonD · Jan 27, 2019

Cab brake light does NOT go thru multi-function switch, direct wire from brake switch

You TEST Fuses and Bulbs, with an OHM meter, "checking" is not specific enough

+1 to Uncle Gump's advice, rear Turn signal bulb and brake light are the same, so if turn signals work then those bulbs are Good and Grounded

Uncle Gump · Jan 27, 2019

I've always tried to diagnose electrical issues looking for a single point of failure. So power to the brake light switch the brake light switch itself or the brake light circuit at the brake light switch would be the single point that would cause all the brake lights not to work.

If it were the multifunction switch... there would be another point of failure to cause the chmsl not to work.

Not saying there isn't dual failures... but it is typically not likely.

kburley · Feb 10, 2019

hey everyone, sorry for the late reply. i replaced all the bulbs after finding a burnt one (weird because the FIRST thing i checked was bulbs) and then i had the 3rd light working but no rears. i swapped the multifunction switch and got all 3 back.

thanks for all the help gentlemen.

RonD · Feb 10, 2019

Good work

Thanks for the update, it may help others

need electrical diagram for brake lights desperately...have no brake lights

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