Help - no brake lights!!
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Senior User
Joined: Jun 2004
Posts: 208
Likes: 1
From: Brooklyn, NY
Help - no brake lights!!
I have a 1994 Extended Aerostar. My brake lights stopped working.
I tested the brake light switch. Interesting, it also controls the Parking Shift lock (or whatever it is called) so that without the switch I could not shift into drive, but the switch is working for that.
I checked the fuse, which according to the owners manual also controls the dash lights (I think). The other lights are working, and the fuse looks good.
The tailligths and blinkers are working. The Brake light bulbs are all good.
Help!!
I think at this point I need someone to tell me where the wiring runs (and the colors if possible,) for me to start physically tracing them to see if there is a break somewhere?
I tested the brake light switch. Interesting, it also controls the Parking Shift lock (or whatever it is called) so that without the switch I could not shift into drive, but the switch is working for that.
I checked the fuse, which according to the owners manual also controls the dash lights (I think). The other lights are working, and the fuse looks good.
The tailligths and blinkers are working. The Brake light bulbs are all good.
Help!!
I think at this point I need someone to tell me where the wiring runs (and the colors if possible,) for me to start physically tracing them to see if there is a break somewhere?
Elder User
Joined: Dec 2004
Posts: 718
Likes: 0
From: North Jersey, New Jersey
So you have checked both parts of the brake switch (the shifter solenoid release and the brake light section) and you had continuity?
Then the switch is ok I would check for a bad ground on the brake lights unless somehow as you said the line has broken somehow.
Then the switch is ok I would check for a bad ground on the brake lights unless somehow as you said the line has broken somehow.
Thread Starter
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Senior User
Joined: Jun 2004
Posts: 208
Likes: 1
From: Brooklyn, NY
The switch looked pretty simple - two wires go in, and when the spring is compressed, the circuit is closed.
I removed the connecter and jumped the two wires. The shifter became unlocked without having to press the brake pedal, but the brake lights did not go on. Is there something else that controls the lights? What 2 parts?
I even removed the switch, but staring at it did not tell me anything.
I removed the connecter and jumped the two wires. The shifter became unlocked without having to press the brake pedal, but the brake lights did not go on. Is there something else that controls the lights? What 2 parts?
I even removed the switch, but staring at it did not tell me anything.
Post Fiend
Joined: Apr 2005
Posts: 5,720
Likes: 5
From: Washington state
the Brake On Off switch BOO is a SPST 1 in 1 out switch controlling ie feeding 12v to the brake lights, the AWD system, the RABS, the shift lock, the PCM and the shift lock....sooo if one is working switch is ok
is your high center stop light working....uses the same ground as the side stop lights?
switched 12v brake runs from common point on Lt. green from C259 pin16 left front inside bottom cowl to C401 P8 located LH rear corner of cargo area, front of LH "D" pillar, forward of rear lamps..... lt. green runs from C401 to each brake light
common ground G101 is located >Front of LH fender apron, left of battery
blk wire
it's all covered here click
dl and burn .iso cd....Aero in Truck .iso's
is your high center stop light working....uses the same ground as the side stop lights?
switched 12v brake runs from common point on Lt. green from C259 pin16 left front inside bottom cowl to C401 P8 located LH rear corner of cargo area, front of LH "D" pillar, forward of rear lamps..... lt. green runs from C401 to each brake light
common ground G101 is located >Front of LH fender apron, left of battery
blk wire
it's all covered here click
dl and burn .iso cd....Aero in Truck .iso's
Last edited by 96_4wdr; Oct 31, 2006 at 06:05 PM.
Mountain Pass
Joined: Jun 2003
Posts: 208
Likes: 3
From: Norfolk VA
Wow! That is a complete description! I hate to say it but it also a little technical for the average guy. Here is something easier.
SPST = Single pole single throw a.k.a. a simple single connection switch
Go to your brake light light with a voltmeter. Make sure your head lights are turned off. Remove the bulb. With someone stepping on the brake pedal look for 12vdc on any of the connections. If 12v is present then your ground is bad. No 12v then start looking at the connectors 96_4wdr described.
I am not sure but I think the rear tail lights won't turn with the head lights if the ground is bad.
SPST = Single pole single throw a.k.a. a simple single connection switch
Go to your brake light light with a voltmeter. Make sure your head lights are turned off. Remove the bulb. With someone stepping on the brake pedal look for 12vdc on any of the connections. If 12v is present then your ground is bad. No 12v then start looking at the connectors 96_4wdr described.
I am not sure but I think the rear tail lights won't turn with the head lights if the ground is bad.
Thread Starter
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Senior User
Joined: Jun 2004
Posts: 208
Likes: 1
From: Brooklyn, NY
Thank you very much 96_4wdr and DOUG5G. Both of you gave me very useful info, and yes, I am technical enough to benefit from the instructions. I will try to ground the wire from the rear to check for voltage first, since that is the shortcut option.
After that I will put a tone N' Probe set to work on the light green wire.
Thanks also for the link to the service mauals. That looks very useful - but after browsing some of the material in them, I think FTE has much better answers!!!
After that I will put a tone N' Probe set to work on the light green wire.
Thanks also for the link to the service mauals. That looks very useful - but after browsing some of the material in them, I think FTE has much better answers!!!
Thread Starter
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Senior User
Joined: Jun 2004
Posts: 208
Likes: 1
From: Brooklyn, NY
Okay, the saga is over.
This morning, armed with all of the wiring diagrams printed out, and a 12v test light, I got to work. First, I pulled off the brake on/off switch and jumped it with a paper clip (I was working alone, and had no one available to step on the brake pedal.) Then I unscrewed the left rear lights and pulled out the stop light bulb. It looked a little corroded. I tested the contacts to ground, and what a surprise - power!! So I repeated that with the right rear lights, and got the same result! So, shaking my head in amazement I pulled out the paper clip, ran to the store, bought new bulbs for all three brake lights, came back and installed them (after cleaning the contacts.)
I nearly fell off my feet when they all lit up. After the fact I examined the bulbs and found corrosion in between the glass and the base. The filaments looked okay.
What a weird coincidence!! Anyway, happy ending but it had me stumped for little while.
Thanks everyone for your help!
This morning, armed with all of the wiring diagrams printed out, and a 12v test light, I got to work. First, I pulled off the brake on/off switch and jumped it with a paper clip (I was working alone, and had no one available to step on the brake pedal.) Then I unscrewed the left rear lights and pulled out the stop light bulb. It looked a little corroded. I tested the contacts to ground, and what a surprise - power!! So I repeated that with the right rear lights, and got the same result! So, shaking my head in amazement I pulled out the paper clip, ran to the store, bought new bulbs for all three brake lights, came back and installed them (after cleaning the contacts.)
I nearly fell off my feet when they all lit up. After the fact I examined the bulbs and found corrosion in between the glass and the base. The filaments looked okay.
What a weird coincidence!! Anyway, happy ending but it had me stumped for little while.
Thanks everyone for your help!
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Postmaster
Joined: Sep 2003
Posts: 4,452
Likes: 1
From: Southern California
Confucius says: "Replace bulbs before tracing circuits." 
Thanks for sharing the outcome, Yitzy.
Thanks for sharing the outcome, Yitzy.
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Lead Driver
Joined: Sep 2003
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From: SoCal
At least check the bulbs before anything else; it's the easiest.
When my brake light filaments burned out, it caused the ABS system to stop working, and disabled the 4wd lockup, torque converter lockup, AND the cruise control. Had me chasing gremlins for a while.
When my brake light filaments burned out, it caused the ABS system to stop working, and disabled the 4wd lockup, torque converter lockup, AND the cruise control. Had me chasing gremlins for a while.
Former ******
Joined: Nov 2004
Posts: 4,901
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From: Salt Lake City, Utah
I've got a strange issue. All my lights work, but when I turn on the hazzard, the right side lights don't blink unless I also turn on the right hand signal. What part would be bad? Also the lights on the trailer behave the same.
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