Intermitant stop lights

[smithe1811]

I'm having some issues with my brake lights. sometimes the work, and sometimes they don't, the tail lights and hazards and turn signals work, just not the stop lights. a good schematic would help or if anyone else has had this issure some info would help too. thanks!

 

Erik :beerhead:

[mvusse]

Since the turn signals use the same filaments on the same bulbs, the sockets, bulbs and most wiring are out of the equation. I would suspect the brake pedal switch.

[smithe1811]

since I'm not a manche master yet, I'm going to assume that would be located under the dash by the pedal?

[SomeNew Name]

could be a grounding issue? check and see if the ground is nice and tight and contacting bare metal.

[fiatslug87]

Here are the diagrams for the brakelight switch from the 1990 FSM. Orientation is different for manual and automatic.

Edit: replaced picture with one showing both manual & automatic orientations.

[mvusse]

The bake light switch is mounted on the pedal itself, near the top. Removing the lower dash trim will make access a lot easier.

 

Edit: Damn Fiatslug87, you're fast!

[fiatslug87]

Edit: Damn Fiatslug87, you're fast!

I have Photoshop open and the FSM and scanner right next to me whenever I check the board just in case.:papers:

[smithe1811]

i just pulled the switch out, thing liike pretty corroded, off to autozone for a new one! thanks for the info, i'll let yall know if it works or not.

 

Erik :beerhead:

[smithe1811]

:headpop: new switch did not fix it, i also replaced the plug for the switch..nothin, i hit the plug with a multimeter and got 10. something, that sound right? any way, i tested the blue wire all the way(i started in the back :nuts: ) from the lights up to where the harness goes into the cab and got nothing, so i guess its a bad wire in the cab somewhere, any ideas where i should look first to save some time? this is my DD so working stoplights are kind of a must.

 

 

Erik :beerhead:

[mvusse]

Could you test the plug with a test light? Volt meter have a very high impedance, and can show voltage when there is barely any power. A test light will tell you more in a case like this.

 

And 10V is not good assuming your batter is around 12V. How much resistance do you need to show a 2V drop against a volt meter? If the battery is at only 10V, you might want to charge it.

 

I looked over the wiring diagrams, and it looks like it is a simple circuit from the fuse block to the switch to the turn signal switch. On the plug, A should be hot (12V), it is marked "20 18PK", I'm assuming PK means pink. B is the other side other side of the switch "71 18LB/BK" which I assume is light blue/black. It goes through the turn signal switch to the lamps. It connects to the hazard flasher switch as well, but does not go through.

 

After the turn signal switch it shows a connector/plug marked A through F with A and E being the stop light/turn signal lamps. But it doesn't show where the connector is located.

 

I hope this is of any help.

[fiatslug87]

I can e-mail you a PDF of the 1988 MJ electrical manual if it would help. PM with an e-mail address if interested.

[djag12]

My light issue was that the PO pulled the wire out of the fuse box and it was just hanging there. Didn't realize what wire it was for until I looked at a schematic.

[smithe1811]

i havent dug into it much since last time, i don't have much time during the week, but i did notice this weird wire that loops out from befind the fuse box and then beck behind it, in the middle it has a 25 amp fuse in a soft plastic holder and its all melted together, the wire looks aftermarket so i didnt think much of it, but now I'm a bit curious if was a rigged up brake light wire :???: dunno. i got a schematic from fiatslug87 i will have to bounce it off of that and see. Diane you probably know more than i do, maybe i'll just give you my truck for a while and throw some cash in there! I'm just kidding, that would take all of the fun out of it!

 

Erik :beerhead:

[ORCA]

Sorry to hijack, and I know it's been awhile since i've been here...

 

fiatslug87, do you have any schematics on the tail light wiring? My turn signals and brakelights are all boogered :roll:

 

PS if you could email the PDF for the electrical manual that'd be great too

 

Thank you ! Again I apologize about the hijack. :hateputers:

[dakal]

had that issue today after firing up my truck after a spell. the switch that touches the brake petal was moving back and forth on its holder . so i zip tied it to it holder. no more problem, unless i can think of a better way, or have some time to mess with it it stays that way :USAflag: .

[djag12]

Erik

 

I was going crazy also looking for my brake light issue. All other lights worked after I sanded down the rusty ground behind the rear driver side tail light. I think there must have been a meltdown by the looks of some of my wires by the fuse box. I plan on trying to pull it out and see if any other damage is there so that I don't have any future issues. Seems like wires melting is common in the MJ. Did you try cleaning up your ground in the tail light it could be as simple as that.

[smithe1811]

thats the thing, I'm not getting any power from the cab back to the lights, so it gotta be in the dash somewhere i think.

 

Erik :beerhead:

[smithe1811]

SUCCESS!thanks to fiatslug87 sending me the schematic from the FSM and absolutely no thanks at all to Haynes, in fact EFF Haynes right up the A! problem was just a recessed connector in that terminal on the steering column, where the blue/black wire connects to the white one. I have stop lights again! thanks again fiatslug87! :cheers:

 

Erik :beerhead:

[fiatslug87]

problem was just a recessed connector in that terminal on the steering column, where the blue/black wire connects to the white one.

Glad to hear you tracked it down. :cheers: I HATE electrical problems. :wall:

[87mjdriver]

could you elaborate on where you found the problem?

I have the same issue right now.

 

bypassed the brake pedal switch and still nothing.

I have tail lights, no brake lights or turn signals or reverse lights for that matter, but I think that is a seperate issue.

allen

[mvusse]

could you elaborate on where you found the problem?

I have the same issue right now.

 

bypassed the brake pedal switch and still nothing.

I have tail lights, no brake lights or turn signals or reverse lights for that matter, but I think that is a seperate issue.

allen

 

If you have no brake OR turn signals, they use the same filament on the same bulbs.

 

Stupid question, but did you check the bulbs?

 

If it is the wiring, it will be between the turn signal switch and the bulbs, not between the brake switch and turn signal switch like Smithe1811.

 

Do the front turn signals work?

[87mjdriver]

replaced both rear bulbs. one was totaly messed up.

and the front blinkers don't work either.

 

where is the turn signal switch. is it the lever you hit to signal?

and previously I had turn signals but no brake lights. now I don't have either.

greatly appreciate the help guys.

[smithe1811]

if you pull off your lower dash, look on the right side of your steering column. there is a big @$$ plug there and if you follow the blue wire from your brake light switch it will go into the top plug where it mates to a white wire. on the side of the plug with the blue wire, where the blue one goes into the plug, there is a little metal connector, it was pulled out just a little bit and not making the connection with the white wire, so all i did was push it back in. does that make sense? I'm tired so if i didnt make a good description i will attempt it again when I'm more awake. :cheers:

 

Erik :beerhead:

[mvusse]

Blown fuses due to a partial short overloading the circuit?

 

I'm just stabbing in the dark now, but it fits the symptoms.

[smithe1811]

yeah mine was just the stop lights, i still had turns and hazards