brake lights

luthpontoo

New member
I have a 03 sprinter . My brake lights quit working . I replaced the bulbs and fuse what else could I be missing . HELP !
 

sailquik

Well-known member
Check the brake light switch at the top of the brake pedal.
There is a "rachet type" adjustment for the switch and it can get
out of adjustment fairly easily.
If I recall correctly, you slide the little rachet plunger out away from the switch
when the brakes are released, so it operates the switch as soon as you press
the pedal.
It only rachets one way, so check to see that when the brakes are released,
you have all the slack out of the rachet.
Here's a link that may help with this adjustment:
https://sprinter-source.com/forums/showthread.php?t=6379
Hope this helps,
Roger
 
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luthpontoo

New member
Thanks sailquik I just tried messing with the switch some , still no lights it could be the switch is bad I have 330,000 miles on this van . would you know how this switch is removed it hard too see and figure out . I dont want to force it and break it .
 

sailquik

Well-known member
Hi luthpontoo,
Unfortunately, I became quite familiar with removing the brake switch when installing my trailer brake controller.
You have to push the switch back toward the firewall to disengage the lock tabs, then rotate the swtich about 30 deg. and it comes right out with
all the wiring attached.
I looked for a photo of the switch, but didn't find anything.
Wish my van was here so I could remove the switch and illustrate the way it locks into place.
Do you have a VOM meter?
Might be good to see if there's 12V at the switch.
If no voltage at the switch (cycle the pedal up and down a bit and hit all the wires) then your problem is probably not
the brake switch.
Also check the fuse panel for in/out voltage on the fuses.
Hope this helps,


Thanks sailquik I just tried messing with the switch some , still no lights it could be the switch is bad I have 330,000 miles on this van . would you know how this switch is removed it hard too see and figure out . I dont want to force it and break it .
 

sailquik

Well-known member
I found a photo of the switch:
Sprinter Brake Light Switch Mount Photo.jpg
As you can see you need to press the lock tab on top down andf toward the firewall, then turn the switch.
Getting it back in you have to push real hard to compress the plastic cone that's outside the center of the switch mount, then turn the switch until the lock tab on the top clicks back into place!
It's been a while, might have to turn it as much as 90 deg. You will know when the two locking dogs let go!
Hope this helps,
Roger


Thanks sailquik I just tried messing with the switch some , still no lights it could be the switch is bad I have 330,000 miles on this van . would you know how this switch is removed it hard too see and figure out . I dont want to force it and break it .
 
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jpoke5

New member
no intent to take over this post but has some good info on my issue. # 5 fuse keeps blowing and cant find the issue. been all over this forum and checked what I could like correct bulbs, short at the tail lights , all three.., inspected wire as best i can and will be in the shop monday for switch replacement. I do think this is a short as its touch and if the fuse burns. started the van and did not move while adding break several times all was fine. went to drive and went about a foot or so and on the third try the fuse went. shut down replaced fuse. started up put foot on break and blown fuse... at one point put a stick on the break and moved around all wires I could find for this system and the fuse did not blow. starting to wonder if this could be a abs controller issue or speed sensor???

any suggestions for this 03 2500 dodge???

Jeff
 

autostaretx

Erratic Member
. started up put foot on break and blown fuse...
Sigh... intermittents are really frustrating to find (especially as you chew through blown fuses)
If (when?) i had this problem, i'd start by NOT replacing the fuse (for the nth time), and by unplugging the tail light unit.
That means you *only* have the wiring in the circuit.
Then i'd attach an ohmmeter to the "load" side of the fuse, with the other end connected to the car's metal.
Now have the assistant stomp on the brakes. Try it with engine running and engine stopped.
If you see the ohmmeter needle (numbers) change, you have a short circuit in the harness to the car's frame.
You could unplug the brake light switch and see if the short is between it and the rear of the car. (most likely)
If you don't see any meter reaction, go and test each taillight unit... *remove* the bulbs, and watch for continuity between the brake light pin and the ground pin. If there's no bulb, there should be no connectivity.
Since driving (or motor running) causes everything to vibrate/jiggle, a static ohmmeter test may not find the culprit.
The above tests (especially with an intermittent symptom) may not show anything, but they're better at locating the cause (cable? fuse block? tail lamp unit?) than guessing and blowing fuses.

Remember to NOT have the ohmmeter in-circuit on a POWERED circuit... it'll blow the meter. With power, you'd only use the voltmeter function.

good luck hunting
--dick
 

220629

Well-known member
A similar method I started using is to take a fairly heavy 12 volt lamp (maybe 21watt?) and attach it across the contacts of a blown fuse. Plug the attached lamp into the fuse position which has been blowing. The lamp will glow brightly with a dead short and less bright with the load of the system lamps on it. It's not entirely foolproof as too many lamps in the system can make it glow fairly brightly under normal conditions, but usually there is a discernable difference in brilliance.

It saves blowing a bunch of fuses during testing. It is also easy for someone to just watch while the stuff Dick suggests is tried. FWIW. vic

Sigh... intermittents are really frustrating to find (especially as you chew through blown fuses)
If (when?) i had this problem, i'd start by NOT replacing the fuse (for the nth time), and by unplugging the tail light unit.
That means you *only* have the wiring in the circuit.
Then i'd attach an ohmmeter to the "load" side of the fuse, with the other end connected to the car's metal.
Now have the assistant stomp on the brakes. Try it with engine running and engine stopped.
If you see the ohmmeter needle (numbers) change, you have a short circuit in the harness to the car's frame.
You could unplug the brake light switch and see if the short is between it and the rear of the car. (most likely)
If you don't see any meter reaction, go and test each taillight unit... *remove* the bulbs, and watch for continuity between the brake light pin and the ground pin. If there's no bulb, there should be no connectivity.
Since driving (or motor running) causes everything to vibrate/jiggle, a static ohmmeter test may not find the culprit.
The above tests (especially with an intermittent symptom) may not show anything, but they're better at locating the cause (cable? fuse block? tail lamp unit?) than guessing and blowing fuses.

Remember to NOT have the ohmmeter in-circuit on a POWERED circuit... it'll blow the meter. With power, you'd only use the voltmeter function.

good luck hunting
--dick
 

autostaretx

Erratic Member
With the bulb-as-fuse on a long wire, you can be your own "assistant".
I like it (especially the "dim-with-load, bright-with-short" additional test report)

--dick
 

220629

Well-known member
With the bulb-as-fuse on a long wire, you can be your own "assistant".
I like it (especially the "dim-with-load, bright-with-short" additional test report)

--dick
I never took the next step to long wires on the lamp. Great idea. :thumbup:

That said, the long wires should include an in-line fuse on the wire coming off the feed side of the fuse block. Or maybe the safer solution is to fuse both wires so how it's plugged in doesn't matter. vic
 

jpoke5

New member
thanks for the comments... I will check into this... I did unplug both tail lights and still blows the fuse so i assume a short... I dont see any areas of a short on the wires under the truck. I guess I will keep looking...
 

jpoke5

New member
is it correct to assume that the short in my break lights is the hot side wire grounding out to the body. and could I use a jumper wire on the hot wire leading to the rear of the truck to count out shorts along the way that may be covered by the tape?? if I can do this... what color is the hot wire leading back to the brake lights??
sorry Im not real good with my shorts...LOL

thanks!!
Jeff
 

220629

Well-known member
is it correct to assume that the short in my break lights is the hot side wire grounding out to the body.
Almost. It can be the wire itself or anything directly electrically connected to that wire such as lamp sockets, rear light assembly traces, etc. Don't forget that there is also a high mounted brake light unit too.

and could I use a jumper wire on the hot wire leading to the rear of the truck to count out shorts along the way that may be covered by the tape?? if I can do this... what color is the hot wire leading back to the brake lights??
sorry Im not real good with my shorts...LOL

thanks!!
Jeff
I'm not certain what you meant. It is possible to run a new separate wire to replace one that is known to be shorted or open. One problem in doing that is that you need to determine what taps off where in the harness and other parts.


My 2004. Should be the same on a 2003.

Wiring I found:
Tail/Park: L = Gray/Blk, R = Gray/Red
Stop: L = Blk/Red, R = Blk/Red
Backup: L = Wht/Red, R = Wht/Red
Turn: L = Blk/Wht, R = Blk/Grn

https://sprinter-source.com/forums/showthread.php?p=25838#post25838

https://sprinter-source.com/forums/showthread.php?p=99430#post99430

Have fun. vic
 
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jpoke5

New member
yes, was thinking i could install a jumper wire on the hot side from a location up front all the way back to the rear near the bumper. was thinking this way I could tell if the short is located in the wire bundle running under the truck???

If i cut the Stop: L = Red/Blk, R = Blk/Red close to the front as I can, replace fuse and does not blow I can assume the short is from that point on back???

Thanks for the help my friends!!

Jeff
 

220629

Well-known member
...
If i cut the Stop: L = Red/Blk, R = Blk/Red close to the front as I can, replace fuse and does not blow I can assume the short is from that point on back???

Thanks for the help my friends!!

Jeff
Well... yes... but chopping wires kinda sends shivers down my spine. IF you are inclined to do so please do this first. Double and triple check any trailer wiring you may have. Before actually chopping, disconnect the plugs to the right and left tail light assemblies. Disconnect the plug to the high brake light assembly. Then try a new fuse and your brake while moving test. If the fuse doesn't blow then stop because the problem is probably in one of the units you unplugged.

If the fuse still blows, then chop one wire, then do the moving brake light test. If the fuse blows then it's in the other wire. If it doesn't blow then MAYBE (because your problem is somewhat intermittent) you have isolated down to that wire and anything still connected to it. Good luck. vic
 

autostaretx

Erratic Member
The *other* problem with just "replacing" the shorting wire is that the original wire is in a cable/bundle.
And that bundle is (obviously?) being worn/chafed through by something sharp.
So jumping around it with a new wire will certainly (we hope) fix *this week's* problem...
but who's to say whether or not *next week* will find the tail or turn signal wire finally getting cut through?
You can fix the symptom, or you can dig harder and fix the cause (put rubber on the sharp edge, smurf tube around the cable, or reroute the cable).

The existing cable could also have suffered invisible damage: something like a thrown rock (or vehicle jack) squashing it enough to cause the individual wires' insulation to be compromised, and perhaps bringing the brown wire's conductors into contact with the stop light's conductors. You won't necessarily see the damage externally.
The good news on such damage would be that it would be unlikely to repeat (so future chafing isn't a problem).
The bad news is that when it's not *quite* fully shorting out, the wires involved may be heating up, melting adjacent wires' insulation, too.

But i must admit that i'm torn.... cutting and jumping around the shorting section is a valid way of dealing with it. As Vic suggests, i'd feel better if i did further diagnosis (cut one wire first, test), or (since it's probably a pain to run the wires, you might as well run both at once). You could cut one wire up front... and bridge the cut with a lower-rated fuse. If that fuse pops, you've found the guilty wire.
What you haven't yet determined is if it's in the circuit leading *to* the brake switch, or in the long cable heading to the rear (most likely, i agree).
Do you have a trailer connector? Has *that* wiring gotten damaged?

good luck
--dick
 
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jpoke5

New member
ok, I will disconnect the upper light and re test... didnt try that yet.
did do the other two. If the fuse blows I will... one at a time cut the wires at the rear to start.
will update.
 

jpoke5

New member
The *other* problem with just "replacing" the shorting wire is that the original wire is in a cable/bundle.
And that bundle is (obviously?) being worn/chafed through by something sharp.
So jumping around it with a new wire will certainly (we hope) fix *this week's* problem...
but who's to say whether or not *next week* will find the tail or turn signal wire finally getting cut through?
You can fix the symptom, or you can dig harder and fix the cause (put rubber on the sharp edge, smurf tube around the cable, or reroute the cable).

good luck
--dick
sure I agree with a good fix... just trying not to spend three days right now pulling apart all them wires and looking things over. I just really want to locate the trouble area and get hauling loads.. Once I know where the trouble is for sure I can plan a good fix... I rather find the trouble then to let the dealer @ 100.00 an hour.
 

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