Brake lights not working

Tiny
TOM COSWAY
  • MEMBER
  • 1985 DODGE RAM
  • V8
  • 2WD
  • AUTOMATIC
  • 180,000 MILES
My brake lights on my truck have stopped working.
I have replaced the bulbs, changed fuses in the fuse box none of witch have helped the problem.
Turn signals and rear lights work, so do reverse lights, just not brake lights and hazards.

Any help would be greatly appreciated.
See attached a picture of my fuse box.
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Monday, October 23rd, 2017 AT 3:42 PM

26 Replies

Tiny
PATENTED_REPAIR_PRO
  • EXPERT
Using a voltmeter or at least a twelve volt test light check the voltage going into and out of the brake light switch for voltage with the brake pedal pressed down a few inches. It is usually found under the dash on the brake pedal.
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Monday, October 23rd, 2017 AT 4:20 PM
Tiny
PATENTED_REPAIR_PRO
  • EXPERT
This should be the wiring diagram and the wire colors are gray going in and white coming out. The fuse is #9 it appears.
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Monday, October 23rd, 2017 AT 4:23 PM
Tiny
MADCOWSCARNIVAL
  • MEMBER
  • 1999 DODGE RAM
Electrical problem 6 cyl Four Wheel Drive Automatic 130000 miles

My brake lights quit working a few days ago. All other lights on the truck work. The cruise control works. The bulbs have been tested, they work, the brake controller (aftermarket) has been tested, it works. The brake switch was replaced twice. After that, I diagnosed the leads into the switch. There is NO constant hot into the switch (I believe there should be - pink wire w/ blue(I think) tracer). There is no power coming into the switch at all. I believe dodge sends the brake switch HOT through a multi function switch. Is there a diagram available for this that can be posted? Can the multi function switch be tested? It is a $110 part so I do not want to replace without being sure. The Chilton manual wiring schematics are worthless and very incomplete.

In addition the wiring schematic from the multi function switch to the fog lights would be appreciated, those have not functioned for several years. The lead that grounds out when activated, does not fully ground out (minimal voltage remains).

Vehicle, more specifically that above is a 1999 Ram 2500 Diesel. It is a half year vehicle in that it uses a brake switch from a 2000 Ram.
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Thursday, July 18th, 2019 AT 6:30 PM (Merged)
Tiny
JDL
  • EXPERT
That is ignition feed, pink wire/dark blue tracer, to the brake switch, goes hot when you turn on the key, there is also a fuse, this info says fuse c 20 amp. If there is a junction where that feed comes from, other than the ignition switch.

Here are a couple of guides and diagrams (below) that will help you get the problem fixed.

https://www.2carpros.com/articles/how-to-check-a-car-fuse

and

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

Please run some tests and get back to us we are interested to see what it is.
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Thursday, July 18th, 2019 AT 6:30 PM (Merged)
Tiny
MADCOWSCARNIVAL
  • MEMBER
Thanks but I need the internals of the switch and before the switch so I can check the power in and jump the switch as a test. Also, am I viewing the pictures the wrong way?

This is exactly what I'm looking for.
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Thursday, July 18th, 2019 AT 6:30 PM (Merged)
Tiny
JDL
  • EXPERT
Hello again, after my morning coffee, I think the brake lights should work, even with the key off. I looked at a couple of databases on the diesel. I think that circuit should be hot all the time. The ignition switch shouldn't have anything to do with it.

The wiring diagram me and you both looked at, does show that fuse circuit goes hot, with the key on.
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Thursday, July 18th, 2019 AT 6:30 PM (Merged)
Tiny
MADCOWSCARNIVAL
  • MEMBER
Jdl, thanks. I will take a close look at the most recent diagram. It definitely should be hot at all times (coming into the brake light switch). I don't think its necessarily the ignition switch that's a problem, I've seen several places that the lead runs through the multi-function switch, that's what I want to jump. However, it goes through another box between the multi-function switch and brake switch. That's what I need to figure out.
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Thursday, July 18th, 2019 AT 6:30 PM (Merged)
Tiny
AXL67356
  • MEMBER
  • 1984 DODGE RAM
  • V8
  • 2WD
  • AUTOMATIC
  • 100,000 MILES
I have problem with a 1984 dodge ram that runs fine only problem brake lights don't work. I have already tested all other lights and they work fine. New bulbs, checked fuses, blinkers work, reverse lamps work, tail tights work. No brake lights when you press on the brake. Replaced the brake switch thought it may be faulty, no change to the problem, still no brake lights.
Chased lines no noticable breaks and the lines look good. Any other suggusetions would be greatly appreciated.
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Thursday, July 18th, 2019 AT 6:30 PM (Merged)
Tiny
JDL
  • EXPERT


http://www.2carpros.com/forum/automotive_pictures/170934_better_diagram_1.jpg



Is that any better? The diagram I was looking at, I increased the magnification, before I copied, then posted. That fuse is located in the power distribution center.
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Thursday, July 18th, 2019 AT 6:30 PM (Merged)
Tiny
M_H_RITZEL
  • EXPERT
Using a test light start at the brake switch and check for voltage on both wires the one going in from the fuse box and the one comming out. If ok then move to the brake light socket and check each one. If you have voltage when the brakes are put on but the lights not lighting when the brakes are put on then check for loose or a bad ground wires. If you don't have voltage comming from the brake light switch to the lights using a test light check to see if there is a broken wire.
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Thursday, July 18th, 2019 AT 6:30 PM (Merged)
Tiny
MADCOWSCARNIVAL
  • MEMBER
Jdl,

Could you also post that same schematic for a 2000 Dodge (blown up in two parts). Some, not all of the wire colors correspond to what I have. The stop switch is most definately from a 2000 dodge though as my truck is some mid-year hybrid.

Also, if you can, where do you get these diagrams? If it is from a technical service manual, I'll happily get one of my own.
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Thursday, July 18th, 2019 AT 6:30 PM (Merged)
Tiny
JDL
  • EXPERT


http://www.2carpros.com/forum/automotive_pictures/170934_better_better_diagram_1.jpg



I'm not sure that will help much. I was looking at a power distribution wiring diagram. There's more than one page. When I magnify a diagram, I have less of the diagram on the screen. I can only copy what the screen shows.

If your county has a large local library, they should have automotive databases, if you live in a county that they serve, some of their databases, you can access from your home computer, for free.

The database I was looking at, ebscohost database. A lot of libraries carry this database. They also carry Mitchel, but, you have to go to the library to access Mitchel.
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Thursday, July 18th, 2019 AT 6:30 PM (Merged)
Tiny
DRLEHR
  • MEMBER
I had that problem with my 2002 diesel 2500. Only the rear tail lights quit. Well The guy at sand lake repair store changed a fues and a relay under the hood. Cost me 45 bucks and it worked ok.

Not sure what fuse or relay. But it was all under the hood not in the cab.

I think the fuse was a 40 because I bought a spare and it is still there as an extra. Not quite a blade style. But a funny colored fues resembeling monopoly houses stacked ontop of each other (green) with a clear window to see the fused metal on the inside.

Sorry Im not technical about this but it fixed my problem.

Damon.
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Thursday, July 18th, 2019 AT 6:30 PM (Merged)
Tiny
WALLACE7777
  • MEMBER
  • 2003 DODGE RAM
  • V8
  • 2WD
  • AUTOMATIC
  • 138,000 MILES
On my 2003 Dodge Ram 1500 W/5.7L, brake lights stay on when ignition is switched to run without the brakes applied and my cruise control does not work. When the ignition is turned off, the brake lights work as they are supposed to. The third brake light works as it is supposed to all the time no matter the switch position. This will happen for a day or two then everything will go back to working for a day or two like it is supposed to then it will mess up again. I replaced the brake switch thinking that may fix it and saw no difference. I have the Complete service manual for my truck and noticed there are three circuits in the brake switch and tested the #4 contact on the brake switch and found no power supply on that wire, I have found this is the Speed Control Supply/Brake Switch No. 2 Signal. It is circuit V32 in the brake switch Pin# 4 V32 20YL/RD SPEED CONTROL SUPPLY/V32 20YL/RD (5.7L) BRAKE SWITCH NO. 2 SIGNAL . The lights started working again for a day and I probed the #4 wire and had power, plugged the connector back into the brake switch and Boom no power and brakes came back on with the ignition switch on and the cruise stopped working again. I have jiggled wires around and don t think I have a short or open where can I check next to trace the problem back? I am thinking this problem is the PCM but I would like confirmation. If it is the PCM, does this have to go to the dealership to be programmed after install or can I just plug it in and go?

Thanks,

Eric
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Thursday, July 18th, 2019 AT 6:30 PM (Merged)
Tiny
CUP1981
  • EXPERT
Hey Eric,

What I am seeing en my schematic is that the brake light switch wires directly into the CHMSL, which is why it still functions just fine. The fault is in one of two places: the instrument cluster, or the PCM. The brake lights run through both of them. The only component that both the brake switch and the cruise control run through is the PCM. By reasonable deduction, I would say it is the PCM. Have the PCM checked by a specialist, they should be able to tell immediately if the PCM has failed or not.
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Thursday, July 18th, 2019 AT 6:30 PM (Merged)
Tiny
KEN
  • ADMIN
Great addition to this thread! Please feel free to help out whenever you are on the site :)

Cheers, Ken
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Thursday, July 18th, 2019 AT 6:30 PM (Merged)
Tiny
WALLACE7777
  • MEMBER
The CHMSL is understood, that is why I was clear that the CHMSL was working correctly. However, the Tail Stop Lights work correctly as well with the iginition off. When the iginition is turned to run is when the stop lights come on and stay on. Does this supply circuit go through the instrument cluster after the brake switch or before? I don't have power to the YL/RD wire #4 at the brake switch and would like to be able to trace it back to the defective source (likely the PCM) before I take it to the dealer and waste money due to a possible break in the wire prior to the connection at the switch.
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Thursday, July 18th, 2019 AT 6:30 PM (Merged)
Tiny
CUP1981
  • EXPERT
Sorry it took me so long to get back to you. This Schematic runs all different directions. What ever happened to power + ground = light :). Anyways. The yellow/red wire that runs from the #4 pin on the brake light switch (Speed Control Supply/brake switch no.2 signal) receives its power from the PCM. Probe pin 14 on the PCM with the ignition off and then on and let me know if there is power coming from there. If not, it's the PCM, if so, I will need to dig farther.
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Thursday, July 18th, 2019 AT 6:30 PM (Merged)
Tiny
WALLACE7777
  • MEMBER
Ok, I had to go out of the country and decided to leave the truck with the dealer. Was contacted and told the TIPM is the problem and claimed they had called Dodge to confirm. $900.00 later I pick the truck up yesterday and brakes are working fine. Go out this morning to head into the office and decided just to take and peak. Brake lights are on again.
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Thursday, July 18th, 2019 AT 6:30 PM (Merged)
Tiny
CUP1981
  • EXPERT
Ok, it sounds like the dealer went the "obvious" route instead of taking the time to really pinpoint test this thing. Try probing the pins I mentioned on March 31 and let me know the result.
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Thursday, July 18th, 2019 AT 6:30 PM (Merged)

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