hi all,

96 ranger xlt 4x4 4.0 auto

ok so the 3rd brake light is on while truck is running. abs light is on also and cruz control stopped working

this problem just started and is driving me nuts, got a used abs control module and replaced both front wheel sensors and the pressure sensor on the master cylinder but the problem wont go away!

the only thing i can think of as a possibility is the brake switch went bad

and before i get flamed for throwing parts at it, this lil truck was rode hard and put away wet before i got her!

thanks in advance

kobin

 

Yes, brake light switch for sure, but rear brakes lights should be on as well, assuming they work?

The 3rd brake light has a direct wire from the Brake light switch to its bulb
The rear brake lights get power from same switch but...............it runs thru the multi-function switch(turn signal stalk) before going to the rear light bulbs

The 3rd brake light can also be the cargo light as well, and if the wires get shorted together 3rd brake light bulb could come in with cargo/dome light problem

Brake pedal switch is also a sensor for ABS, there are two switches inside it, if ABS module see the "brakes on" all the time then it will turn on the ABS light

 

ok cool , thanks ron

all my brake lights work, just the 3rd brake light acts like a running light when truck is running and lights up brighter when pedal is pushed

 

Then 3rd brake light wire has a short to a Key on power source, assuming 3rd brake light goes off with key off?

Brake light switch has power all the time, not key on key off, so if it was a short in the switch then it should be on all the time, and won't change brightness by pushing the pedal

Not sure which side the 3rd brake light wire runs from?

Wait.............If there was a short on the 3rd brake light wire then that voltage should also run to the rear brake lights?

Does it

 

no it dose not, thats why im thinking switch, ron

if i unplug the switch and light went out, its the switch? and how many wires go to the switch? 2? or more than 2?

 

Yes, only other thing that comes to mind is that another system is using the 3rd brake light's Ground, that cause the bulb to glow, not as bright as direct 12v but lights up

Could be switch as well

 

ok i did a couple of test.

first i looked at the lights key off engine off=no lights

next key on engine off no lights except 3rd brake light

next unplugged brake switch at pedal key on engine off 3rd brake light still on

next left said switch unplugged then unplugged pressure switch at master cylinder key on engine off 3rd brake light still on

my next test will be to unplug drivers side rear light assy to see what happens but that will be tomorrow afternoon

 

ok ron everything i can think of is not working

i checked all fuses they are good

cruz malfunction somewhere? just replaced button pods on steering wheel awhile back,

what else is tied to abs and cruise control?

 

4x4 uses brake light switch so GEM module in 1996, but don't see an ABS connection

Shift interlock as well(allows you to shift out of Park when foot is on the brakes)

 

what if i unplug the third brake light? should the abs light stay on? what if it goes out?

some where there has to be a junction to tie every thing to the brake switch. there are only two wires on the switch its self

 

Since the 3rd Brake Light (BL) is on low, could indicate a bad ground somewhere close but what is up that high.

Were the doors open when you check the 3rd BL ?
Thinking out loud here..., sometimes the 3rd BL has a Cargo Light in it that operates with the doors and when actuated by the Headlight Switch thumb Wheel, if the door switch was shorted in one of the doors... could that feed back to the Cargo Light through the ground to the Brake Light Wires.
Not sure if the power to the Cargo Light is Power-On all the time.

If there is a connector to the Door Switches, disconnect the Switches one at a time and see what happens.

Luck / Ltr

 

scrambler, it has separate bed lights and they work as expected. they never come on when door is opened. they do come on with dimmer wheel.

hmmmm i did a dome light swap out of a mustang recently, ill unplug it and let you know.

 

ok now i wait a half hour, dome light, 3rd brake light is unplugged pos and neg terminals are off the batt and touching.

ron, would the instrument cluster have any thing to do with it?

 

No, instrument cluster doesn't really have any connection to brake light wiring
Its brake warning light(red) is connected to Parking Brake switch, and Master fluid level switch, fluid level is also connected to ABS module, so low fluid can turn on Red Brake warning light AND Yellow ABS warning light

 

so while i was waiting, i took a work truck to the parts store to get the sensor for the rear end. 20 bucks later and i am home again. all hooked up but no joy! boooo

ill put the rear sensor in and let yall know tomorrow when i get off work

now im thinking multi function switch on column

 

now that i think about it, i dont remember if any red lights came on with key

 

ok update time, abs dash light is off now, replaced all speed sensors, brake pedal switch and the control module

still no cruse control and third brake light is still on.

im going to disconnect the cruse pods, maybe they went bad, they were used.

i guess ill just have to open the wallet a little more and get new ones

 

Cruise can't activate with brake light on, and you are getting voltage on the 3rd brake light wire even if its not coming from brake light switch, so Cruise with see that and not activate

It would be possible for cruise module to send OUT 12v to brake lights instead of just monitoring 12v IN from brake lights

Unplug brake light switch and turn on the key, see if 3rd brake light is on

If its on then start pulling out Cab fuses, one at a time to see if you can find the circuit thats providing the 12volts

 

wow thanks ron! i haven't had to pull fuses in years to troubleshoot something! weekend project "detective" *ques pink panther music*

 

ok update time, its fixed.... cruise works and third brake light is out!

the fix, third brake light had two ground wires, one for third brake light and one for bed lights. when i installed the load leveler resistor as per manufactures rep for the light assy, he assured me the lights were different circuits and the grounds were not connected in the light its self just at the plug. of coarse electricity takes the path of least resistance and wahlah third brake light is on!

i moved the load leveler resister to the truck side of the wiring as it only has one ground wire and poof all is back as it should be

thanks ron and all for the input

 

Good work

But.............what the "load leveling resistor" for?

LEDs?

 

yes ron, led lights

i have replaced all lights with leds