L4310 - Phantom Electrical Short In The Lighting

[rfdfirecaptain]

I have a 2009 L4310 that suddenly lost its headlights, clearance lights and brake lights. I found the 20A fuse was blown and I replaced it. Immediately it blew again. I ohmed out some power wires and they were not shorted, so I decided to order a new light switch and that didn't solve the problem.

I have removed several wires from the switch plug to see if I could isolate the wire that is grounding out. I found a small blue wire with white stripe (top row second from right on wiring harness plug) that appears to feed a number of lights. I have disconnected all lights and the plug that is hidden behind the panel on the ROPS. The blue wire with white strips on the harness plug is still grounding out and it's a bear to visually trace all these wires to look for a rubbed place.

Maybe I have narrowed this down to the wrong wire, but I don't think so since removing this wire from the harness side of the plug is the only action I have taken that stops the 20A fuse from blowing and still allows the headlights to work. Although the headlights are the only lights that work, which are controlled by that 20A fuse.

The bottom line is the blue wire with white strips has continuity with the negative battery cable and the corresponding wire that mates to it comiing from the switch side of the plug has 12v of power when the headlights are switched on... and that is what's blowing my fuse... I think

Any ideas? I'm pretty frustrated at this point and I don't have a wiring diagram. I am working from what information I can learn by using my Ohm meter to test the wires.

The bottom line is the blue wire with white stripe has continuity with the negative battery cable and the corresponding wire that mates to it inside the plug, coming from the switch side has 12 volts of power on it when the headlights are switched on. And that is what I have figured out is blowing my 20A fuse.

 

[Eric McCarthy]

Geez you're like the 4th person on here lately with a wireing/electrical issue with their lights. So far everybody has asked questions but no body has yet to report back a solution to the problem.

 

[Stumpy]

I'd definitely agree you've found your problem source. I think your next step is to bypass that wire, replace it point to point with a wire of the same gauge. It may be a bit iffy without a wiring diagram but call your dealer. Ask them if you can photo copy the wiring diagram out of their service manual, if they have half a brain they'll say yes knowing they just secured your business.

 

[rfdfirecaptain]

Thanks Matt! With no wiring diagram... just guessing here, this wire splits about 5 ways, possibly more then runs to each lighting device. If I could find the place where all these individual wires on this circuit are spliced together I could hopefully isolate the section of wire that's grounding out. Unfortunately that's not as easy as it sounds. Hard to see.. hard to get to... just not an easy task when you're blindly looking for a splice.

I bought it new from a dealer who is about 100 miles away casue my local dealer was an ass... who eventually went out of business. No surprise there! I was hoping at the very least someone could tell me where to find the splice so I could start trying to isolate the bad section of wire. I doubt the wiring diagram is going to tell you exactly where to look on the harness to find the splice.

 

[dmanlyr]

Perhaps I mis understand the test you did, but did you completly disconnect the blue with a white sripe wire at every connection? Unless you disconnected the blue with a white stripe wire at each light, you will see contnuity thru the wire to ground as the filiments in the lights are going to show that.

Of course it will not be continuity without some resitance, but depending uppon the meter type and the range selected, it could appear to have full continity leading one to beleive there is a short to ground, when it is just the normal filiment restance to ground.

? David

 

[rfdfirecaptain]

Good point David. Yes, I completely disconnected each lighting device on this circuit including the harness plug that is hidden behine the driver's side ROP beauty panel.

Now that you mention it I did not disconnect the lighting for the instrument panel. Not sure where that is exactly. But, my Ohm tests are coming up with all ZEROS... it's reading the lowest resistance possible.

 

[rfdfirecaptain]

With no responses I've had to resort to sheer determination to fix this thing. I don't have it repaired yet, but I have located the problem. Getting to it to make the repair will be the trick.

Today I made sure all lighting devices were disconnected I even disconnected the instrument panel. I set my Ohm meter to "tone" put one contact on the Negative battery post and the other on the Blue wire with White Strip. With all lighting devices off the circuit I still had tone which means this wire was grounding out. I decided to start removing the wiring harness paying close alltention to all corners and bends.

I started by removing the narrow-curved beauty panel off the driver's sidedoor jamb. I was able to get the section of the wiring harness that runs up to the top of the cab completely exposed down to the flooring. After flexing it a hundred times I still had tone.

So, I crawled underneath the tractor and pulled this part of the wiring harness down through the flooring. Within seconds I lost tone. I tried to wiggle and giggle to see what part of the wire is grounding out. As best I can determine the problem is in the section of wife that runs back up through the flooring over toward the ingntion switch where is ties into several other pigtails of the wiring harness.

So, now I have a new question for this forum. Does anyone have any expeirence removing a wiring harness like the one of this L4310? If so, how about a few pointer or tricks you have learned???
Thanks!