brakes lights stuck on

trooper632

CJ-8 Member
City
sabinal
State
TX
Hello all, I put a new brake master cylinder on the 83 scrambler and the brake lights are stuck on. Brakes work fine but i had to take the bulbs out so the battery wont run down. The brakes are non power manual brakes, any suggestions
 

barrys

Scrambler Junkie
Lifetime Member
City
East Norriton
State
PA
Brake switch is under dash above brake pedal swing arm....if that helps. They are threaded and can be adjusted.
 
Last edited:

b2esq

Scrambler Junkie
Lifetime Member
City
Glen Allen
State
VA
Brake switch is under dash above brake pedal swing arm....if that helps. The are threaded and can be adjusted.

These are both true statements. But good luck getting to (and especialy adjusting) it. It's not rocket science by any stretch of the imagination. It's a simple plunger switch. The plunger end is threaded into the pedal bracket, and the switch end has a 2-wire harness that clips on. Simple stuff... except... you can't get to it when everything is installed wihtout voodoo magic... I hate that switch. I hate that switch. I hate that switch... (I was just working on it this past weekend -- so my nerves may still be a little raw... lol).

But, hey, I'll root for you...

 

bigwalton

Alaskan Postal nutjob
FORUM MANAGER
SOA Member
City
Dexter
State
MI
I hate that switch with the burning fire of hell. :evil:

Not that it helps here, you'll have to deal with it regardless, just be prepared for the suck.

The easiest time I've had (and that's relative) is when I had the drivers seat out and could lay down more easily (also relative.)
 

Craner8

CJ-8 Member
Silver Member
Member
City
Orlando
State
FL
X10 on the switch. Hard to reach. If you have a/c, easiest I found was to unbolt dash and lay it back against column. Easy access then. Sounds like a lot but it's a huge time saver really.
 

Spieg

Scrambler Junkie
Lifetime Member
City
Aurora
State
CO
Totally agree that switch is a biatch! I'm guessing your switch may be okay since it was working before the new master cylinder. Does the brake light go off if you physically lift the brake pedal as high as it will go? If so then the switch is working and you just have an adjustment/position issue.

If the switch does work, I'd double check your master cylinder to make sure it is installed/functioning correctly. For some reason your pedal is not being returned enough by the new MC.

If you do need to make an adjustment, you can actually bend the metal plate on the brake pedal that contacts the brake switch enough to make a small adjustment rather than adjusting the switch position (much easier).
 

bigwalton

Alaskan Postal nutjob
FORUM MANAGER
SOA Member
City
Dexter
State
MI
X10 on the switch. Hard to reach. If you have a/c, easiest I found was to unbolt dash and lay it back against column. Easy access then. Sounds like a lot but it's a huge time saver really.

Dear God, I can't even fathom dealing with it with A/C :eek:
 

bigwalton

Alaskan Postal nutjob
FORUM MANAGER
SOA Member
City
Dexter
State
MI
Totally agree that switch is a biatch! I'm guessing your switch may be okay since it was working before the new master cylinder. Does the brake light go off if you physically lift the brake pedal as high as it will go? If so then the switch is working and you just have an adjustment/position issue.

If the switch does work, I'd double check your master cylinder to make sure it is installed/functioning correctly. For some reason your pedal is not being returned enough by the new MC.

If you do need to make an adjustment, you can actually bend the metal plate on the brake pedal that contacts the brake switch enough to make a small adjustment rather than adjusting the switch position (much easier).

This is truth right here, I didn't really think it through in the red rage that came on when I read about dealing with that brake switch. It could be a matter of needing to adjust the brake rod or switch with the switch being fine. I had this happen on the tail end of the trip back from the National Scramble in Alabama. I ended up rigging a bungee to the brake pedal arm to pull it up fully because the brake lights were staying on.

Ended up being able to put a couple turns on the brake rod and fixed it.
 

MrBeep

CJ-8 Vendor Supporter
SOA Member
CJ-8.com Vendor
City
Dillsboro
State
IN
Young children (grandkids) with small fingers and hands work well also. I had a spare swing assembly and could demonstrate how I needed it turned. Only took 2 hours and a trip to the Dairy Queen. :wave:
 

jsteed

CJ-8 Member
City
Seattle
State
WA
Mine does this as well. I found that the pedal return spring was not strong enough at times to return the pedal. pull up on your brake pedal and see if that makes the lights go off. if it does, consider just replacing spring with a tighter one as this will be a lot easier than replacing the godforsaken switch.
 

Cmath

Scrambler Enthusiast
Lifetime Member
SOA Member
City
Woodstock
State
Ga
Messed with the switch once . Replacing the spring is my go to now.
 

Kane

CJ-8 Member
City
Berlin
State
ct
If you replaced the master cylinder most likely the pedal is sitting a tad bit lower now than before and/or you might be missing your return spring on the brake pedal arm. You can adjust the switch as other have stated or you might be able to bend the tab on the brake level to get it to close the switch.
 

SgtMajHarper

New member
City
Peyton
State
CO
Greetings........I'm new to the site, long time Jeep and also Scrambler owner. I've had "some" of the usual issue with mine over the years, but have managed to stumbled though until now. I have the same "I hate that switch-switch" issue. I finally popped the dash, lowered the steering column, reached inside underneath and upside down with my gorilla hands and fat fingers and found a plug with a 2 wire coupler coming from the brake light switch, later determined to be for a cruise control another writer said and a 3rd wire that was cut and all 3 were hot. So I got the switch out "eventually" and hooked up the new one an yes it works when using a test light and seems to be adjusted correctly.

Odd thing is, no brake lights come on, I have working emergency flashers so the bulbs and wiring going back "should be good". The fuse isn't blown.......I'm befuddled. I'm thinking about using the one cut wire that goes hot when brake pedal pushed and running a new wire back to the brake lights ??? Wish I knew what that wire was supposed to go to......voodoo magic under the dash in wire spaghetti land.
 

FLCJ8

Legacy Registered User
City
Palm Bay
State
FL
Odd thing is, no brake lights come on, I have working emergency flashers so the bulbs and wiring going back "should be good". The fuse isn't blown.......I'm befuddled. I'm thinking about using the one cut wire that goes hot when brake pedal pushed and running a new wire back to the brake lights ??? Wish I knew what that wire was supposed to go to......voodoo magic under the dash in wire spaghetti land.
Welcome to the site.

The brake light wiring goes through the multi-function switch (turn signal) after leaving the brake light switch.
If you bypass that and run a separate wire to the rear brake lights there will be no easy way to have functioning rear turn signals, as well you will have issues with a back feed to your front turn signals when the brakes are applied.

mfs.PNG



The full sheet is thumbnailed below.
 

SgtMajHarper

New member
City
Peyton
State
CO
Good copy on all of that, thanks much. I'm gonna play my dumba$$ card on this.......am looking for a shorted wire, something came loose or just replace the thing and cross my fingers? If that don't fix it, what other voodoo could there be? I hope it's warm enough next week to get back at it.
 

FLCJ8

Legacy Registered User
City
Palm Bay
State
FL
I just reread your original post and saw that you dropped the steering column...
the wiring to the MFS has a connector on the side of the column, it's possible that it got jarred loose.
Do you know if the old switch was defective?

I suggest using your test light and follow the current flow from the brake light switch through the connector at the column to see where the circuit loses power.

mfs.PNG

From your previous remarks that your rear hazards work I would suspect that the wire from the brake switch to the "P" at the connector is having problems, either at the connector or internally at the MFS.

The wiring for the brake lights and hazards are the same leaving the MFS to the rear lights so if the rear hazards work properly I would suspect the wire from the brake switch to the "P" terminal is the source of the problem.

The brake light switch and hazard power both connect at the MFS, I'm just not certain how.

I had written a long step by step trouble shooting post with the highlighted points on the diagram, but think this would be your best place to start.

Perform the testing with the turn signal lever in the neutral position, brakes depressed and hazards off.

Also, if you get voltage at "P" but the brake lights still don't work, remove the hazard flasher and engage the hazard switch while the brake is still depressed.
Check for voltage at "K". If you don't get voltage there the connection internally at the MFS is open.

If the brake lights still don't work you can run a temporary jumper from a known hot to "M" and "N" individually to check the brake light functions on the back.

Sorry if this is confusing, I suck at typing as well as explaining the rationale of the steps.
 

SgtMajHarper

New member
City
Peyton
State
CO
Thanks much for the detailed info., I need a warmer day off to go out and see if I can work thru your checklist.

To answer a couple questions you had, yes, I determined that the brake light switch was bad....once I was able to reach it I put a test light on it and I had hot tires coming out of it going to the cruise control wire on both sides, also both sides of the wires to the brake light switch were hot at all times. Once I replaced the bake light switch, I had hot / cold wires like I should and the new switch functions properly.

I already had the brake light switch issue before dropping the steering column and it seemed to only move down "maybe a couple of inches"? It could have worked something else loose I guess, anything is possible when grabbing around under there with big hands and fingers in tight places.

I'll hopefully be able to get back at it next week and see what I can find....thanks again, great info.
 
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