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Brake light woes after bulb change

W

Woodswanderer

NAXJA Forum User
Location
SEPA
99 4.0 aw4 sport.

Upgraded to LED brake light bulbs. Worked fine as a red marker light, except when i stepped on the pedal it wouldnt light up like a brake lamp should.

Pulled LED bulbs, installed standard halogens, they lit up in the parking lot but still no brake lights when i push the pedal. Got home, right side isnt lighting up at all now, save reverse and turn signal lamps.

The 3rd brake light has been out for a bit, worked fine with an led 194 bulb in it, then nothing when i stepped on pedal, now nothing at all. Regardless of what bulb is in there.

All fuses have been removed and reinstalled, no bad fuses. Wtf is going on here?


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Headlight switch is new, connector was fine when i replaced it. Only thing i can think of is the brake pedal switch is toast or something in the wiring is screwed.

Can anyone tell me, do the brake lights run thru the big white main power block behind the center console/driver knee panel? Its possible that worked its way loose since the heater core/dash removal job


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What is the condition of the contact points inside the sockets? Clean and shiny or tarnished/crudded up? If not clean and shiny, well, clean it up. Electrical contact cleaner and a small brush or a bit of Scotch Brite on the end of a screwdriver or some such thing may be helpful.

If clean and shiny, test at the socket for continuity to ground (that would be the contact to the outer rim of the bulb on an old style, metal based bulb. Not sure what it is on the new style bulbs that just have wires folded over the glass/plastic base. Not sure which style is in a '99.). If no continuity to ground, then work your way back to the ground connection.

If you have a good ground where you are supposed to, then get someone to depress the brake pedal and test for 12V on the supply line at the socket. If no 12V, then work your way through the system to figure out what is wrong.

It sounds like you haven't been playing around with anything else in the system, so I would expect to find your problem at the sockets. A poor connection inside the socket is at the top of my list for probable culprits. We had a similar issue with The Varmints' '97 ZJ. Along with cleaning the connections I added a very conservative thin smear of OX-Gard on the contacts. Not much--it is conductive (that is the point) and if it reaches from one contact to another it would be a short in the system. It has been good for about a year now. The goal is to put on just enough to protect the contacts from oxidation.
 
Contacts look good, i’ll try cleaning them up again. Factory used a 3157 wedge bulb on 99MY

As far as the brake light itself goes, it very well coupd be the switch at the pedal. I seem to recall reading that its a common failure item. Still doesnt explain why my right rear worked fine (marker lamp, no brake lamp) then 10 miles later nothing.

Kinda gettinf pissed off at this jeep and contemplating setting it on fire to buy a truck that’ll tow better


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I've been converting rear lights to LED for what must be best part of 20 years & never had an issue, including my '98 XJ, & never had an issue, so doubt they're the root cause of the problem.

One possibility is that you can put these wedge bulbs in backwards which means you probably wouldn't notice the difference in brightness with the brakes applied.

However, as the 3rd brakelight doesn't work either, I'd suspect the switch, so pull the wires off & jump them & if brakelight come on - replace the switch.

I suspect the right tail light out is coincidence, swap bulb with the left one, see if the fault moves; if it does, replace the one now on the left.
 
I need to replace the right side housing anyhow now. The lower tab that holds it tight to the body snapped off.

I did flip the polarity around on the brand new halogen bulb, no good. Still wont light up. The LED bulbs are polarity free canbus compatible from Auxito (to keep from hyperflashing brake lights). I’ve had really good luck and no problems with their led bulbs


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The only thing I couldn't change out (otherwise full interior/exterior) was the front side markers on my 2000.
 
Brake light switch fixed the brake lights, including high mount. I still dont have right rear marker lamp though. I’ll swap the LEDs back in and see what happens, not really necessary with these candlepower krypton 3457 bulbs im using 😉 40w/10w halogens 🤣


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As an aside, the duralast switch from the zone has a plunger on it that is about 1/4” longer than the old 200k mile part

Brake pedal no more sponge 🤣


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RCP Phx said:
Just to clarify, I tried some leds in the side marker but it caused a problem with some kind of backfeed/cross-circuit.
Click to expand...

I did a little write up about my experiences putting LED's in.
I had the same problem with ones that had polarity.
Excerpt from my write up:

Problems started with the 194's in the side markers. Remember that LED's have polarity.

So putting it in one way resulted in this:
Would go on with headlights.
Would blink when using the turn signals when the headlights were on.
Would not blink when using the turn signals with the headlights off.

Putting the bulb in the other way resulted in this:
Would not light up when you turned on the headlights.
Would blink when you used the turn signals with the headlights off.
Would not blink when you used the turn signals with the headlights on.

Those I linked are not "Polarity Sensitive".
How they worded it in the specs. LOL.
 
Interesting that you guys are having issues with the side marker/turn signals. Mine have been flaky too. Left side works fine with 194 led installed, right side has never worked properly and at first would cut power to both sides id i smacked it (like loose connection/bad ground) while using an led bulb. Standaed halogen bulbs dont work either.


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More developments: the entire right side marker lamp circuit is dead. Front, side, rear. Nothing


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Fixed. Im a dumbass and blind. Fuse 23 in cabin that controls right marker lamp xircuit was installed on gang 24


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Woodswanderer said:
I need to replace the right side housing anyhow now. The lower tab that holds it tight to the body snapped off.

I did flip the polarity around on the brand new halogen bulb, no good. Still wont light up. The LED bulbs are polarity free canbus compatible from Auxito (to keep from hyperflashing brake lights). I’ve had really good luck and no problems with their led bulbs


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Click to expand...

I found on my '96 that I couldn't refit the housings without breaking off those tabs - but no such probs with the later models.

It wasn't polarity I had in mind but the fact there are 2 completely different bulbs that look the same & will physically fit. One has the +ive & -ive terminals opposite each other, the other has the +ive for each filament opposite each other, which means you can accidently swap over the running lights & brake lights.
 
XJI6191 said:
Not sure I like the idea of 40w halogen bulbs in all plastic housings.
Click to expand...


Its 40w brake 10w marker. They are (now defunct/discontinued) Candlepower Krypton 3457 bulbs. They are krypton filled glass inside of a plastic/polycarbonate outer lens

Im going to swap back to the LED bulb and compare them side by side, then go from there. Really want lower power consumption of the Leds


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If they have a plastic/polycarbonate outer lens I guess they can't get that hot, which was my concern, perhaps krypton burns cooler than halogen.

Thing I like about LED's in rear lights in particular is that not only are they very bright but very red (received wisdom is behind coloured lenses to always have LED's the same colour)
 
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