Archived Wire Harness Wows

[ChrisSmith]

For the last month I've battled a short somewhere on the truck in the Parking Lamp circuit. I've read lots of threads from TDR and all suggested checking bulbs and connectors for water or corrosion and like many members, I could find no obvious sign of a problem.



Well today I promised myself I was goind to find the root of the problem if it meant tearing the entire truck apart. Luckily it didn't. What I did find was if I singled out the parking light circuit to only the front of the truck (left and right lights were the only ON loads, no relays in PDC) and then slowly bent the large wire harness coming from the cab firewall, I would see a 25 Amp spike hit the meter and "POOF" there goes the 15A fuse. I swear I could also hear sounds of arcing occuring within the wire harness! So far, the parking circuit is the only one effected, but this certainly doesn't sound good for the other 50 wires in the bundle!



Has anyone ever troubleshot an electrical short down to this particular wire harness, and what luck did anyone fixing it?



Chris Smith

1997 3500

 

[jrobinson2]

If you have recently installed batterys that are not as tall as the original ones, (usually Optima's) without using spacers or shortening the hold down bolts the outside driver side bolt can go right through the main harness. On my father in laws '96 it shorted the park lights.

Jared

 

[ToolManTimTaylor]

Hang On lemmie Page Holeshot. He has been THE MASTER at Parking light issues.



https://www.turbodieselregister.com/forums/showthread.php?t=112170





Look at the seccond post from the last!!

 

[HoleshotHolset]

Check out the area of that big honkin' bundle-o-wires that runs underneath the ABS stuff... mine was shorting out against the bracket that supports the ABS stuff.



It's hard to get in there to see it... but that's where my short was. I found it the same way - jiggle test.



Matt

 

[ChrisSmith]

Wire Harness Failure

Thanks for the suggestions everyone.



My particular electrical short was occuring where the main cab/engine compartment wiring bundle is routed over the driver-side wheel-well. It looks like the wiring bundle had been chaffing for a good while and eventually wore through the "athletic tape", electrical tape, and finally parking circuit wire insulation (14 gage black with yellow stripe). Supprising enough there was NO plastic conduit around the wire bundle where the short happened (see attachments). Also the plastic zip-tie fasteners supporting the wire bundle were designed too low on the fender, allowing the bundle to come into contact with the wheel-well.



In my opinion, the root cause of failure was due to a weak mechanical design with the routing of this wire harness because clearly this was a potential chaffe point that was overlooked by the design engineer. I have no information as to what truck models or years are suseptatble to this problem. The wire harness on my truck was made in Thailand (identified by the part sticker located just above the W/H 90 deg bend), and assuming that their assembly repeatablility is consistent, the Parking Light Circuit may be the most suseptable wire in the bundle to this failure. I see no reason, however, that any OTHER wire in the bundle could not have been the symptom as a result of the chaffing. I inspected all of the bundle wires at this location and luckly the Parking Light circuit was the only one effected.



If anyone is experiencing intermittent, high current, or seemingly unexplainable circuit shorts they need to take a look at this area of the wire bundle. Once identified, so long as multiple wires are not effected, an easy solution would be to re-wrap the bundle using plastic conduit (or any hard plastic material- I used the side of a laundry detergent bottle) on the underside which will help protect the wire bundle. This is however not exactly a permanent fix as chaffing could still occur depending on the amount of vibration the truck experiences. The best solution is to suspend the harness so that it does not make contact with the wheel-well at all, but this is not the easiest fix. As for me, I did both.



I hope this helps some people. Please pass it along as needed.



Regards,

 

[HoleshotHolset]

I'm starting to wonder if Daimler Chrysler or the NTSB should be notified about this... I knew my '98 wasn't the only one that could have this problem.



Matt