General Technical & Electrical General technical and electrical discussion for the Ford Ranger that does not fit in any other sub-forum.

Tail lights stay on, Parasitic drain.

  #1  
Old 03-15-2019
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Icon4 Tail lights stay on, Parasitic drain.

Hello all, first post on the Forum. Im having some electrical problems. Im pretty savvy when It comes to my truck, but have been stumped the past couple days. Problem is all my rear lights stay on even when the key is out. Left light, right light, and third brake light. Ive already tested my battery and its fine at a solid 12.9V. I then tested for parasitic drain with my meter and get a pull of about 4.9A coming from somewhere. Started pulling fuses and only one that turns the lights off is #26. Its a 10A fuse for Battery Saver Relay, Auxillary Relay Box, Restraint Central Module (RCM), Generic Electroic Module (GEM), and Instrument Cluster. Stuck, Need help!

-Truck is a 2002 Ford Ranger 4.0 4x4
 
  #2  
Old 03-16-2019
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Sounds like you have a bad/sticking brake light/stoplight switch. Its activated when you hit the brakes. Bad switch thats sticking will cause brake lights to stay on. Your "third" cab brake light staying on is a dead give a way that it's not in your light switch, but in your brake light switch.
Not sure where it's located on a 2002, but most likely under the dash near the steering column. Look for a switch thats activated when you depress the brake pedal.
Depending on the make/model, can be fairly cheap to replace. Could also be a missing little rubber bumper that is attached to the brake pedal that when the brake pedal is released, compresses against the switch to close the sircuit, cutting power to the switch.
If that bumper is missing, the brake lights will stay on.
If you google up "2002 Ford Ranger brake light stays on" much info will come up including you tube of how to fix.
Very simple repair and cheap.
Grumpaw
 

Last edited by Grumpaw; 03-16-2019 at 05:09 AM.
  #3  
Old 03-16-2019
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Go under the dash, by the brake pedal and pull a wire off the Brake Light Switch and see if they go off.

If not, wondering if the Multifunction Switch (MFS) inside of the steering column is shorted out; the MFS controls Brake Lights, Directionals, Flashers, and who know what else.
 
  #4  
Old 03-16-2019
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Scrambler, the multi function switch operated everything you listed, xcept the brake lights. Their on a seperate circuit. He also stated the brake lights were on with the ignition off which would eliminate the multi switch. Also, his 3rd brake light on would eliminate the multi switch.
My bet is the brake light switch.
Grump
 
  #5  
Old 03-16-2019
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Yes, +1 ^^^^

For sure brake light switch on brake pedal

It has battery voltage all the time, not a key on/off circuit

And 3rd brake light is directly wired to the brake switch


Fuse #26 will shut off power to the brake light switch and the other devices you listed, so for sure brake light switch

And Fuse 26 will draw power for 20-30minutes after key off/doors closed, that is normal, its a power off timer in GEM module, "battery saver relay timer"
It cuts power to most electrical systems in the cab except for keyless entry and KAMs

If you want to test power drain then you have to hook up meter to the battery and then wait for 30+ minutes and then check for amp draw, .03-.07amps is expected after the 30 minutes
That draw is from computer, radio and keyless entry
 

Last edited by RonD; 03-16-2019 at 10:55 AM.
  #6  
Old 03-16-2019
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The Brake Light wire goes through the MFS, IF you have Brake/Directional Lights.
The MFS makes the decision when the directional lever is positioned and allow one brake light to come on and the other light will flash.
The third brake light..., I do not know how that works except that it come on when you press the brake pedal.

Let me qualify, that is the way I thought it worked.
 
  #7  
Old 03-16-2019
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Yes, that is correct, but 3rd brake light doesn't, it is direct from brake switch to light bulb

Around 2000 Rangers switch from 2 bulb tail lights to 1 bulb, at that time the brake/turn shared one filament in the bulb, other filament was parking light
This is when multi-function switch(MFS) could come into play if there were brake or turn signal issues
But 3rd brake light was still direct from brake pedal switch

Two bulb setup had a separate turn signal bulb, the dual filament bulb was for brake and park lights
It was just cheaper to loose the extra bulb and wires, so thats what Ford did
 
Attached Files
File Type: pdf
1999 exterior lights.pdf (58.5 KB, 3 views)

Last edited by RonD; 03-16-2019 at 11:02 PM.
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