Brake light problem - help
Thread Starter
|
Laughing Gas
Joined: Jan 2005
Posts: 1,055
Likes: 3
From: Magnolia, TX
Brake light problem - help
Hey Guys,
Just purchased today a 2001 ST 4.0 2WD with 55K miles. I'm going throug all the paces of maintenance, etc.
Problem: driver's side brake light does not get voltage to the bulb socket. Passenger socket and trailer harness both get 12.X volts when brake pedal is pressed. Maybe a few millivolts on the driver's side.
Can a faulty brake pedal stop-light switch do this?
Thoughts?
CMOS
Just purchased today a 2001 ST 4.0 2WD with 55K miles. I'm going throug all the paces of maintenance, etc.
Problem: driver's side brake light does not get voltage to the bulb socket. Passenger socket and trailer harness both get 12.X volts when brake pedal is pressed. Maybe a few millivolts on the driver's side.
Can a faulty brake pedal stop-light switch do this?
Thoughts?
CMOS
Cargo Master
Joined: Aug 2003
Posts: 3,263
Likes: 92
From: BC Canada
The power for the brake lite, power distribution box > fuse > switch on brake pedal > common wire to the tail lights... so there has to be a bad connection between the brake pedal and the light socket.. check where the trailer harness adapter connects with the main harness,
Thread Starter
|
Laughing Gas
Joined: Jan 2005
Posts: 1,055
Likes: 3
From: Magnolia, TX
A little more info:
Forgot to add that the driver's side turn signal doesn't work (which is expected as it's the same bulb). Parking lights DO work on both sides, sothe issue is within the brake/turn signal bulb circuit.
How do I check this? The harness is secured up un the body of the truck. Can I check this wire/circuit somewhere up in the front end of the truck?
Am I correct that the brake bulb filament and turn signal filamant are on e and the same in the dual filament bulb? Correct?
CMOS
Forgot to add that the driver's side turn signal doesn't work (which is expected as it's the same bulb). Parking lights DO work on both sides, sothe issue is within the brake/turn signal bulb circuit.
How do I check this? The harness is secured up un the body of the truck. Can I check this wire/circuit somewhere up in the front end of the truck?
Am I correct that the brake bulb filament and turn signal filamant are on e and the same in the dual filament bulb? Correct?
CMOS
Cargo Master
Joined: Aug 2003
Posts: 3,263
Likes: 92
From: BC Canada
Originally Posted by CMOS
A little more info:
Am I correct that the brake bulb filament and turn signal filamant are on e and the same in the dual filament bulb? Correct?
CMOS
Am I correct that the brake bulb filament and turn signal filamant are on e and the same in the dual filament bulb? Correct?
CMOS
I will have a look at the schematic to see what you have to follow(circuit),
Thread Starter
|
Laughing Gas
Joined: Jan 2005
Posts: 1,055
Likes: 3
From: Magnolia, TX
Originally Posted by aquanaut20
You are correct, either the 12vdc is not arriving or the ground on the rear light is no good.
I will have a look at the schematic to see what you have to follow(circuit), but doesn't the 2001 have a separate bulb for the turn signal(amber)??.
I will have a look at the schematic to see what you have to follow(circuit), but doesn't the 2001 have a separate bulb for the turn signal(amber)??.
Any help will be appreciated.
Again - no 12V is getting to the TS/Brake wire.
CMOS
Trending Topics
Posting Guru
Joined: Jan 2001
Posts: 1,124
Likes: 1
From: Rural Florida Panhandle
If you checked for voltage with voltmeter, I assume it had a good ground.
This would eliminate the bad ground possibility. However, just because the tail light works does not necessarily mean the ground is good. Sometimes when the ground is open, the tail light current will return through the brake light. You may have seen a vehicle in front of you which has a tail light until the brakes are applied, then the tail light goes out (and no brake light). This is indicative of a poor ground.
I too, thought there were separate bulbs for the turn and brake, but don't have any tech info to check it out. My 02 Mountaineer has separate bulbs, and they are both 3157 dual filaments.
This would eliminate the bad ground possibility. However, just because the tail light works does not necessarily mean the ground is good. Sometimes when the ground is open, the tail light current will return through the brake light. You may have seen a vehicle in front of you which has a tail light until the brakes are applied, then the tail light goes out (and no brake light). This is indicative of a poor ground.
I too, thought there were separate bulbs for the turn and brake, but don't have any tech info to check it out. My 02 Mountaineer has separate bulbs, and they are both 3157 dual filaments.
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
3 Best / 3 Worst Parts of Modern Ford Ownership
Brett Foote
10 Amazing Upgrades That Solve Common Ford Truck Owner Headaches
Pouria Savadkouei
Every 2026 Ford Engine Explained
Brett Foote
10 Ugly Ford Trucks That We Still Kinda Love
Joe Kucinski
10 Things Every Truck Owner NEEDS (2026 Edition)
Michael S. Palmer
Rezvani's Latest Post-Apocalyptic Monster Is a Ford F-150 Raptor Underneath
Verdad Gallardo
Top 10 Most Expensive Ford Trucks Ever Sold on Bring a Trailer
Joe Kucinski
2027 Ford Super Duty Buyer's Guide (Every Model, Engine, & Package)
Brett Foote
Top 10 Ford Truck Tragedies
Joe Kucinski
Thread Starter
|
Laughing Gas
Joined: Jan 2005
Posts: 1,055
Likes: 3
From: Magnolia, TX
Some more info - the problem is intermittant. It's been working for the last few days but began to act up again today.
No fuses have been blown so there's not a short. Sounds more like an intermittant connection issue.
Any suggestions?
CMOS
No fuses have been blown so there's not a short. Sounds more like an intermittant connection issue.
Any suggestions?
CMOS
Cargo Master
Joined: Aug 2003
Posts: 3,263
Likes: 92
From: BC Canada
Originally Posted by CMOS
Some more info - the problem is intermittant. It's been working for the last few days but began to act up again today.
No fuses have been blown so there's not a short. Sounds more like an intermittant connection issue.
Any suggestions?CMOS
No fuses have been blown so there's not a short. Sounds more like an intermittant connection issue.
Any suggestions?CMOS
Hotshot
Joined: Jan 2004
Posts: 19,763
Likes: 1,082
From: St Louis
Lots of inaccurate information due to lack of proper reference material.
Each of the lines for rear brake/stop lamps goes all the way to the Central junction Box. It is spliced to a fuse which feeds the trailer harness. This is fed from the MFS on the column.
If would be helpful in isolating the fault if you can determine if the fault occurs simultaneously at the trailer connector.
If both exhibit the fault, the problem is between the CJB and the to/in the MFS.
If it's only the LR corner and the tow harness is good, then it's a faulty feed line between the CJB and the LR corner.
Steve
Each of the lines for rear brake/stop lamps goes all the way to the Central junction Box. It is spliced to a fuse which feeds the trailer harness. This is fed from the MFS on the column.
If would be helpful in isolating the fault if you can determine if the fault occurs simultaneously at the trailer connector.
If both exhibit the fault, the problem is between the CJB and the to/in the MFS.
If it's only the LR corner and the tow harness is good, then it's a faulty feed line between the CJB and the LR corner.
Steve
Thread Starter
|
Laughing Gas
Joined: Jan 2005
Posts: 1,055
Likes: 3
From: Magnolia, TX
Originally Posted by projectSHO89
Lots of inaccurate information due to lack of proper reference material.
Each of the lines for rear brake/stop lamps goes all the way to the Central junction Box. It is spliced to a fuse which feeds the trailer harness. This is fed from the MFS on the column.
If would be helpful in isolating the fault if you can determine if the fault occurs simultaneously at the trailer connector.
If both exhibit the fault, the problem is between the CJB and the to/in the MFS.
If it's only the LR corner and the tow harness is good, then it's a faulty feed line between the CJB and the LR corner.
Steve
Each of the lines for rear brake/stop lamps goes all the way to the Central junction Box. It is spliced to a fuse which feeds the trailer harness. This is fed from the MFS on the column.
If would be helpful in isolating the fault if you can determine if the fault occurs simultaneously at the trailer connector.
If both exhibit the fault, the problem is between the CJB and the to/in the MFS.
If it's only the LR corner and the tow harness is good, then it's a faulty feed line between the CJB and the LR corner.
Steve
Good info. I'll check this out.
CMOS
Thread Starter
|
Laughing Gas
Joined: Jan 2005
Posts: 1,055
Likes: 3
From: Magnolia, TX
UPDATE 3-9-08
The problem is somewhere in the steering column.
When the tilt wheel is in the highest positon, it works fine. In any of the other positions the light problem ocurrs.
Also, if the steering wheel is in the highest position and I grab the 12 o'clock position of the wheel and apply some downward pressure, the lights malfunction.
So, do y'all think the problem is in the turn signal switch itself, or some part of the harness?
How do I remove the covering that is over the steering column so I can take a peek?
Thanks,
CMOS
The problem is somewhere in the steering column.
When the tilt wheel is in the highest positon, it works fine. In any of the other positions the light problem ocurrs.
Also, if the steering wheel is in the highest position and I grab the 12 o'clock position of the wheel and apply some downward pressure, the lights malfunction.
So, do y'all think the problem is in the turn signal switch itself, or some part of the harness?
How do I remove the covering that is over the steering column so I can take a peek?
Thanks,
CMOS
Cargo Master
Joined: Aug 2003
Posts: 3,263
Likes: 92
From: BC Canada
Such that the problem changes when you move the tilt, my first inclination would be a wire that is chafed, second the multifunction switch. The top of the column cover can be removed by endoing the screws fom under the bottom section, this will give access to MFS and harness.
DO NOT disturb the air bag, safest to pull fuse and let sit for 20min. Not sure which fuse in yourswithout looking at schematic.
DO NOT disturb the air bag, safest to pull fuse and let sit for 20min. Not sure which fuse in yourswithout looking at schematic.