Has anyone here done a complete wiring harness replacement?

Rod Midkiff said:
I like the idea of doing both, and I often do when doing tail lights on a trailer.
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Definitely. Lots of the little low current stuff will be fine if done properly via the monocoque. In the X where the battery is far removed from the starter/alternator, I reckon a decent lead, battery neg to starter earth gives an engine bay earth stud for key stuff with minimum loss. Well worth the effort and dare I say, weight!
 
Another change I am doing. Aside from the fuses in the fuse block [item 24 in image], I have an inline fuse [item 23 in image].
1707109763121.png
This inline 8A fuse supplies/protects cigar lighter, clock, radio antenna and courtesy light. It receives power from a connection to a bus bar on the in side of the main fuse block. That bus connects to the dreaded brown wire connector. All good. But notice that fuse slots O and P in the main fuse block, attached to the same bus, are not in use. So, delete the inline fuse [I hate inline fuses] and connect to the out side of fuse slot P [or O] and insert an 8A fuse, I get this.
1707110230847.png
Which is functionally identical - but less wire, easier fault finding :)
 
Regarding the additional ground cable idea. I see both sides of this; I agree with Dom that it really shouldn't be necessary, but I also agree that it certainly wouldn't hurt. The X does have a longer than usual distance between the battery and the major charging system components, but a short run to the main fuse/relay box. I suppose it may come down to personal preference, unless there is a specific need for it. For example on my current build I will be using a aftermarket standalone ECU to control the fuel and ignition. The instructions for that ECU highly suggest that you run a dedicated ground cable from the battery solely for the ECU. That might be a little overkill but they have their reasons for requiring it. Although for a stock vehicle with a electrical system in good condition, proper wire harness, clean ground connections, etc, I don't think there is any reason for a additional ground cable. But as I said earlier, it would not hurt anything other than adding weight. Perhaps adding a lighter medium-gauge cable (rather than a really heavy one) may be a decent compromise?
 
Well, on the distance thing. Most race cars have the battery in the trunk, and they don't seem to have trouble with long battery cables.

Also, on Semi's, Most of them have dedicated ground wires from the ECU to the batteries. So that Tells Me that it is an important step.

(FYI, there are many UNFUSED wires on a semi) they are saving money by not installing them. So you know they cut any/all corners that they can. And they are installing dedicated ground wires.
 
Dr.Jeff said:
Regarding the additional ground cable idea. I see both sides of this; I agree with Dom that it really shouldn't be necessary, but I also agree that it certainly wouldn't hurt. The X does have a longer than usual distance between the battery and the major charging system components, but a short run to the main fuse/relay box. I suppose it may come down to personal preference, unless there is a specific need for it. For example on my current build I will be using a aftermarket standalone ECU to control the fuel and ignition. The instructions for that ECU highly suggest that you run a dedicated ground cable from the battery solely for the ECU. That might be a little overkill but they have their reasons for requiring it. Although for a stock vehicle with a electrical system in good condition, proper wire harness, clean ground connections, etc, I don't think there is any reason for a additional ground cable. But as I said earlier, it would not hurt anything other than adding weight. Perhaps adding a lighter medium-gauge cable (rather than a really heavy one) may be a decent compromise?
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It would be easy to determine if a ground cable would make a significant improvement. All you need is an ohmmeter that has good accuracy and resolution for low resistance values. Measure the ground resistance between the two locations. Whether it is good enough will depend on your criteria for acceptable voltage drop (V=I * R). If it is not good enough, add a cable with low enough resistance to get you where you need to be.
 
easy to tell if you need to improve your earth. For a given component, say the ECU, run a fat cable, eg jump cable, from battery -ve to voltmeter and other end on the earth of the ECU.

Best to do this while cranking the engine (pull the coil HT lead to make sure it does actually start.

If you see a significant value on your meter, then you need to improve your earth. If not what you have is good enough.
 
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