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View Full Version : 03 Sprinter #5 fuse keeps blowing


qroberts7
03-15-2016, 09:55 PM
Hey everyone, I have a 2003 sprinter 2500 that currently has 212k on it. I've been driving it around for 6 months now and haven't had too many issues outside of some routine maintenance. I just drove the van back home to NY from Oregon and didn't have a single issue the entire trip home. Once i got back however I started having issues with fuse #5. It started a bit intermittently for for the first 3 fuses, could drive it for an hour os so before it would blow again (this was all in the same day.) But after that they would blow the second I would touch the brake. I read through a ton of threads on here and followed the advice of thoroughly checking the underbody wiring harness, i couldn't find any spots where the casing had rubbed away, and i even cleaned up the ground at the very rear of the van. All this time mind you the bulbs in the housing were lighting up but not getting brighter when I pressed the brake. (I used a pen to bypass the shifter being locked up). The next day I started checking the bulbs and noticed one of the middle bulbs was out so I changed it, still no luck. Ordered a new brake light switch and changed it but still no luck. purchased some new bulbs (ended up being the wrong ones) for the taillight housings, still no luck. about this time as well the fuse was still blowing instantly but None of the bulbs in the taillight housing were lighting up at all when the van was turned on. I found the thread about the correct bulbs, purchased all new bulbs for both housings. Replaced them but they still won't even light up when turned on and the fuse is still blowing instantly. I don't know what to do at this point, and would hate to have to bring it to a mechanic to get fixed, So I figured I would try here and see if anyone had any advice. Thanks in advance - Quinn

qroberts7
03-16-2016, 12:16 AM
Also the ASR light comes on as soon as the fuse blows

autostaretx
03-16-2016, 12:46 AM
Step one: unplug both rear light assemblies and step on the brake.

Does the fuse blow?
If not, the problem is in one of the assemblies (perhaps a broken-free copper bus bar)
If the fuse does blow, it's either the wiring or the top center 3rd brake light assembly.
Also verify that the license plate lights are not floating loose and shorting to the frame.

...those are the first steps i'd take...
--dick
p.s. you can download the 2003 service manual (chapter 8W is wiring schematics) from http://aie-services-2.net/Sprinter/

qroberts7
03-16-2016, 02:49 AM
Step one: unplug both rear light assemblies and step on the brake.

Does the fuse blow?
If not, the problem is in one of the assemblies (perhaps a broken-free copper bus bar)
If the fuse does blow, it's either the wiring or the top center 3rd brake light assembly.
Also verify that the license plate lights are not floating loose and shorting to the frame.

...those are the first steps i'd take...
--dick
p.s. you can download the 2003 service manual (chapter 8W is wiring schematics) from http://aie-services-2.net/Sprinter/

Good call and thanks for the manual. I unplugged the taillights and it still blew so time to start digging through wires again.

autostaretx
03-16-2016, 05:47 PM
Good call and thanks for the manual. I unplugged the taillights and it still blew so time to start digging through wires again.
OOkaaay.... here's the brake light circuit: (this might be from the 2006 manual)

74750

Note that Fuse 5 can also be blown by problems in the shifter handle assembly, the anti-lock brake controller, or the lights.

I'd start by unplugging C2 at the brake switch, and stepping on the pedal.
Did it blow? No? Then it's the tail light wiring (or the top brake light)
An ohmmeter between C2's pins and the Sprinter's frame (ground) would help save on cost of fuses during testing.
(don't fry the ohmmeter by accidentally testing the battery-feed pin ... pull fuse 5 or disconnect the battery)

Yes? it's the other stuff (or their wiring).

If Yes (it still blew), then unplug C1 (leaving C2 unplugged) and step on the pedal again.
If it still blows, then ??? (since the switch is now totally isolated)
Since (i hope) it did NOT blow, then plug C2 (tail lights) back in again, and step on the pedal.
If it didn't blow this time (C1 unplugged, C2 plugged in), add the tail light assemblies, step on pedal again.

If it still didn't blow (C2 and all tail lights in place), then it's chase-down-C1 time. Open up C202 if you can find it or "unplug the shift handle assembly" and try again.
(or the anti-lock brake controller)

Inspect and feel the wiring leading to each subassembly. If a wire bundle is internally damaged, you can often feel it as a hard/stiff section along an otherwise bendable (with some effort, perhaps) cable harness.

good luck
--dick
p.s. note that splice S204 goes off-page to 8w-10-20 ... where it's shown as also going to a "data link connector" pin.
Yes, gang... fuse 5 shows up on pin 8 on the OBD socket as the "switched ignition" pin..
Since that's before the brake switch, it shouldn't be part of this problem.

qroberts7
03-17-2016, 04:02 AM
OOkaaay.... here's the brake light circuit: (this might be from the 2006 manual)

74750

Note that Fuse 5 can also be blown by problems in the shifter handle assembly, the anti-lock brake controller, or the lights.

I'd start by unplugging C2 at the brake switch, and stepping on the pedal.
Did it blow? No? Then it's the tail light wiring (or the top brake light)
An ohmmeter between C2's pins and the Sprinter's frame (ground) would help save on cost of fuses during testing.
(don't fry the ohmmeter by accidentally testing the battery-feed pin ... pull fuse 5 or disconnect the battery)

Yes? it's the other stuff (or their wiring).

If Yes (it still blew), then unplug C1 (leaving C2 unplugged) and step on the pedal again.
If it still blows, then ??? (since the switch is now totally isolated)
Since (i hope) it did NOT blow, then plug C2 (tail lights) back in again, and step on the pedal.
If it didn't blow this time (C1 unplugged, C2 plugged in), add the tail light assemblies, step on pedal again.

If it still didn't blow (C2 and all tail lights in place), then it's chase-down-C1 time. Open up C202 if you can find it or "unplug the shift handle assembly" and try again.
(or the anti-lock brake controller)

Inspect and feel the wiring leading to each subassembly. If a wire bundle is internally damaged, you can often feel it as a hard/stiff section along an otherwise bendable (with some effort, perhaps) cable harness.

good luck
--dick
p.s. note that splice S204 goes off-page to 8w-10-20 ... where it's shown as also going to a "data link connector" pin.
Yes, gang... fuse 5 shows up on pin 8 on the OBD socket as the "switched ignition" pin..
Since that's before the brake switch, it shouldn't be part of this problem.

Thanks Dick, I ended up going through the underbody wire harness with no luck, so went through the wiring for the taillights and still had no luck. I took a look at the third brake light from above and everything checked out, so I attempted to close the back door and the top wouldn't latch. I climbed up and sure enough one of the wires from the third brake light had somehow found its way into the path of the upper bar section and I guess I had closed the door enough without noticing to chop through half of the wire. So I cut it, spliced it and taped it all up and out of the way and everything went back to normal! I really appreciate all the information, without it I would probably still be searching.

Thanks! - Quinn

recycledbread
05-16-2016, 09:27 PM
OOkaaay.... here's the brake light circuit: (this might be from the 2006 manual)

74750

Note that Fuse 5 can also be blown by problems in the shifter handle assembly, the anti-lock brake controller, or the lights.

I'd start by unplugging C2 at the brake switch, and stepping on the pedal.
Did it blow? No? Then it's the tail light wiring (or the top brake light)
An ohmmeter between C2's pins and the Sprinter's frame (ground) would help save on cost of fuses during testing.
(don't fry the ohmmeter by accidentally testing the battery-feed pin ... pull fuse 5 or disconnect the battery)

Yes? it's the other stuff (or their wiring).

If Yes (it still blew), then unplug C1 (leaving C2 unplugged) and step on the pedal again.
If it still blows, then ??? (since the switch is now totally isolated)
Since (i hope) it did NOT blow, then plug C2 (tail lights) back in again, and step on the pedal.
If it didn't blow this time (C1 unplugged, C2 plugged in), add the tail light assemblies, step on pedal again.

If it still didn't blow (C2 and all tail lights in place), then it's chase-down-C1 time. Open up C202 if you can find it or "unplug the shift handle assembly" and try again.
(or the anti-lock brake controller)

Inspect and feel the wiring leading to each subassembly. If a wire bundle is internally damaged, you can often feel it as a hard/stiff section along an otherwise bendable (with some effort, perhaps) cable harness.

good luck
--dick
p.s. note that splice S204 goes off-page to 8w-10-20 ... where it's shown as also going to a "data link connector" pin.
Yes, gang... fuse 5 shows up on pin 8 on the OBD socket as the "switched ignition" pin..
Since that's before the brake switch, it shouldn't be part of this problem.

Having the same issue here. I'd like to do this test.

Where do I find C1 and C2?

Stani
08-30-2018, 04:33 AM
C1 and C2 refer to Connection 1 and Connection 2 on the brake light switch. Near the brake pedal is the brake light switch and once removed you can access the electric connections on it.

anon7
11-05-2018, 08:53 PM
Old threads rule!
Have been driving illegally for months. No brake lights at all. I also have one (only one) and at times NO headlights. (more on that below)
Typical #5 fuse blown upon depression of brake pedal. I figured if I got pulled Id open the drivers door, and show the officer the pile of at least 50 blown 10 amp fuses and my fuse pullers and beg for a pardon. Depending on his mood and other factors we wont get into here, I may get a warning. So finally got around today to looking into this further. Spend several days and even bought a new brake light panel back when it first happened to no avail.


I found a picture on here, (no idea which thread or who submitted it) where someone had slid pieces of plastic in the circuit board due to poor insulators. I saved it to my pc. I had checked ONE of the connections, but in my stressed beyond sanity lifestyle, I had missed the second one. The top connection was pushed into the board. I pryed it back with a small pocket knife and slid a small piece of cut to size zip tie between and POW!

Id like to thank whoever I thanked above for the great tutorial in unplugging and testing.

NEXT UP is the headlights!

I had previously installed a set of Nilight 90 Watt LED floods on the bumper, and at night I run them. Other drivers hate me, but oh well. The van is used for emergency repairs. I have to work. Lets see if we can figure out why I have no headlights.... (this should be fun, because Im running LEDs...) Ill report back.


PS would LOVE if someone would list a *REASONABLY PRICED* working LED or HID headlight solution. I have 3) 2004 T1s, One is stock and works great but looks old due to halogens. One is running HIDs (I cut the wire and straight wired the wires to the bulbs) and its MUCH brighter and looks 1000 times better, and the 3rd is running high wattage LEDs. Both that were converted have had the original headlight connectors removed (one just fell off in my hands in a pile of rust.) There has to be an easier way.

anon7
11-05-2018, 09:24 PM
OK at a stand still. Theres a bright yellow wire in the drivers side headlight assembly that is cut and bare. Its not touching anything, but I can't figure out what it goes to. My local Dodge dealership is quite useless. They said they have no wiring diagrams. Seriously? Anyone know?

autostaretx
11-05-2018, 09:38 PM
Yellow is Low Beam (unless you have daytime running lights, in which case it's yellow with a green stripe)..

Per page 8w-50-7 and -8 in the 2006 service manual (http://diysprinter.co.uk/reference/2006-VA-SM.pdf).

--dick
p.s. White is high beam, the browns all go to ground/frame.

billintomahawk
11-07-2018, 01:30 AM
Fuse 12 in fuse block #1 to low beam yellow wire.

(Well Dick , you were faster.)

bill

Aqua Puttana
03-26-2019, 02:40 PM
OK at a stand still. Theres a bright yellow wire in the drivers side headlight assembly that is cut and bare. Its not touching anything, but I can't figure out what it goes to. My local Dodge dealership is quite useless. They said they have no wiring diagrams. Seriously? Anyone know?
Unrelated to brake lights. Scroll to above for Autostaretx Dick's excellent brake circuit troubleshooting overview. :thumbup: Do you have trailer wiring? If yes, check that for problems first.

I know that this an old post. For future reference. The yellow wire in the headlamp assembly is the low beam aka dipped beam lamp feed. I tapped that wire for a temporary headlamp feed when my MFS died.

Some info is here.

Emergency Headlight Power Fix + MFS info
https://sprinter-source.com/forum/showthread.php?t=72680

:cheers: vic

P.s. - The plastic insert repair idea to the rear light assembly was mine. It is still working on my 2004 since 2010.

ABS ESP Traction Lights On Brake Light Fuse (#5?) Blown Shift Locked
https://sprinter-source.com/forum/showthread.php?p=99430#post99430