no brake lights
#1
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Year: 99
Model: Cherokee (XJ)
Engine: 4.0
no brake lights
hey all im trying to get my brake lights back. its a 99 auto
I have pulled out the brake stop switch and tested the pink/blue trace in which has its constant 12v supply.
whit and tan also is supplying 12v until the switch gets pressed in then 12v is cut out. this white wire is sending 12v to the rear of the vehicle and all other lights work, just not the brake filament.
there are three wires to the brake lights, driver side example-black( ground), Brown ( fused left inboard tail lamp) i get nothing on this wire with switch pressed or not, white/tan (brake lamp switch output) again 12v is here when supplied by driving light switch.
the brake stop switch ohms good. the light bult is plastic surround with two metal pins, im not sure how to make the other brake filiment glow here- again driving filament works when 12v runs through.
all fuses are good.
Im a little stuck on what im looking for now guys?
I have pulled out the brake stop switch and tested the pink/blue trace in which has its constant 12v supply.
whit and tan also is supplying 12v until the switch gets pressed in then 12v is cut out. this white wire is sending 12v to the rear of the vehicle and all other lights work, just not the brake filament.
there are three wires to the brake lights, driver side example-black( ground), Brown ( fused left inboard tail lamp) i get nothing on this wire with switch pressed or not, white/tan (brake lamp switch output) again 12v is here when supplied by driving light switch.
the brake stop switch ohms good. the light bult is plastic surround with two metal pins, im not sure how to make the other brake filiment glow here- again driving filament works when 12v runs through.
all fuses are good.
Im a little stuck on what im looking for now guys?
#2
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Year: 1989
Model: Comanche (MJ)
Engine: 4.0
That white/tan wire runs through a few connectors along the way through the body, and arrives at the brake lights as a white/tan wire. Does that have voltage when the brake is pressed (and the switch is unpressed)? You tried a new bulb yet?
#3
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Year: 1998 Classic (I'll get it running soon....) and 02 Grand
Model: Cherokee (XJ)
Engine: 4.0
Oh, come on, Lawson! Do you think he'd overlook something as obvious as that????
Yup, he would. and we've all done it!
#5
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Year: 96
Model: Cherokee (XJ)
Engine: 4.0
use a test lamp
does it light at the brake switch when pressed ?
does it light at the rear socket when pressed ?
If yes then no, the harness is bad somewhere, when I pulled some wires at the rear connector on one of mine, I actually screamed...all the wires had cracked insulation
find the 12V, correct any deficiencies, re-wire if needed
does it light at the brake switch when pressed ?
does it light at the rear socket when pressed ?
If yes then no, the harness is bad somewhere, when I pulled some wires at the rear connector on one of mine, I actually screamed...all the wires had cracked insulation
find the 12V, correct any deficiencies, re-wire if needed
#7
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Year: 96
Model: Cherokee (XJ)
Engine: 4.0
a corroded terminal might pass 12V...at a few mico-amps for instance..so your multimeter will say 12V
try passing 2amp, like a brake light, and it wont...a test light pulls much higher current
I prefer test light for 12V, but not electronics, (due to their low resistance)
try passing 2amp, like a brake light, and it wont...a test light pulls much higher current
I prefer test light for 12V, but not electronics, (due to their low resistance)
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MtnHermit (05-27-2020)
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#8
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- Is there any power at all?
- Does the power drop under load?
- Check to see if the bulb is good.
- Check to see if there's power and how much.
- Check if the power drops under load and how much.
#9
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Year: 99
Model: Cherokee (XJ)
Engine: 4.0
use a test lamp
does it light at the brake switch when pressed ?
white/tan illuminates at the terminal with the test light until the brake switch is pressed.
pink/blue into break switch illuminates always, white/tan again off when switch is pressed.
does it light at the rear socket when pressed ?
negative
with driving light activated- driver/ passenger side terminal has power to white/tan and brown.
If yes then no, the harness is bad somewhere, when I pulled some wires at the rear connector on one of mine, I actually screamed...all the wires had cracked insulation
find the 12V, correct any deficiencies, re-wire if needed
does it light at the brake switch when pressed ?
white/tan illuminates at the terminal with the test light until the brake switch is pressed.
pink/blue into break switch illuminates always, white/tan again off when switch is pressed.
does it light at the rear socket when pressed ?
negative
with driving light activated- driver/ passenger side terminal has power to white/tan and brown.
If yes then no, the harness is bad somewhere, when I pulled some wires at the rear connector on one of mine, I actually screamed...all the wires had cracked insulation
find the 12V, correct any deficiencies, re-wire if needed
Last edited by 4x4jeepmanthing; 06-27-2019 at 06:34 PM.
#10
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Year: 96
Model: Cherokee (XJ)
Engine: 4.0
I am confused..had a quick look at a '95 brake switch diagram..appears there is more than 3 wires..one to TCM and PCM..they may be switch to earth..dunno ?
What I do know is all mechanical brake switches I have worked on switch +12V to the brake lights when the switch is either closed or open, (depending on the design)
therefore, when the pedal is actuated, the switch should close the circuit, allowing 12V to flow out of the switch, down the wire that is identified in the relevant FSM by color, to the brake lights
If this is not occuring, the switch is defective
What I do know is all mechanical brake switches I have worked on switch +12V to the brake lights when the switch is either closed or open, (depending on the design)
therefore, when the pedal is actuated, the switch should close the circuit, allowing 12V to flow out of the switch, down the wire that is identified in the relevant FSM by color, to the brake lights
If this is not occuring, the switch is defective
#12
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Year: 96
Model: Cherokee (XJ)
Engine: 4.0
I use both side by side
for 12V auto electrical, (not electronic), I just find it faster and more certain to start with a test light when searching for 12V+
good example, under dash fusebox
For all other applications, I start with a multimeter
#14
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Year: 1995 RHD
Model: Cherokee (XJ)
Engine: 4.0l
I recently traced fault with tow wiring which had me stumped. At the relay I was reading +12v so at the time I thought the power source was good. It turned out that when you tried to pull power through the relay to power the tow lighting, everything died. In the end there was a bad connector under the van which had corroded causing the issues. The point being, under no load you can get false readings with a multimeter as they can't always show a true reading of a circuit under load. Had I of used my test light, I would have found the issue much quicker.
Hopefully that makes sense, it's 1:26am and I'm off.