[TrickyT]

Originally Posted by Photoman

I’m not sure about that downside. I would ask this question. Does the cruiser run with the battery disconnected? If yes, either the Main 2.0L fusible link or a 150 amp fuse would only protect the small white wire from the battery, not the alternator. In the accident or wire short scenario if the motor was still running it would not matter if either fuse failed as the small white wire would still get output from the alternator. Maybe unregulated.

I think it will run with the battery disconnected. But in this scenario it won't stay running long because the wire in question powers the ECU and if it shorts to ground the ECU will go dead and the motor will stop. So the wiring is self-protected in this case.

Originally Posted by Photoman

TrickyT’s point is well taken. Any alterations we make can have consequences. If this is not acceptable, leave it stock. If concerned about TrickyT’s point with the above wiring option, fuse the small white wire at the alternator.

Before we pull our hotdogs out for the wire test I need to make a couple corrections. I said the small white wire was “about” 10 gauge; it’s actually closer to 7 gauge. The 10 gauge wire is 12 inches away from the “B” alternator terminal. Second the fuse link wire measures around 12 gauge not 14 gauge. I measured the copper now instead of “abouting”, first with an American standard wire gauge and then with a micrometer. They still will not be exact but closer to correct.

The diameters of the wires are as follows:
Main charging larger white wire was .160 inches……..~ 6 gauge
Smaller white wire .140 inches……..~7 gauge
Blue fusible link wire .082 inches…….~12 gauge

12 inches from the “B” post on the alternator the .140 inch smaller white wire has 2 wires bugged on. The diameter of each wire is .100 inches…….~10 gauge One of these wires goes to the under hood 15 amp EFI, the other to the headlight relay.
The .140 inch white wire continues through the firewall to the in dash fuse panel. At least 3 other wires are bugged off this to feed circuits in the fuse panel. 10 amp ECU B, 15 amp OBD, 20 amp defog, and 40 amp FL heater. I did not measure these wire sizes nor look where the splices were. To sum up, an ~7 gauge wire runs from the alternator “B” post in to the in dash fuse panel with at least 5 wires bugged off of it some of them ~10 gauge.

~7 gauge should be good for ~89 amps indefinitely according to the chart. And like any copper wire, it will probably handle much more than this for a short period of time. In the short-to-ground scenario it needs to handle a whole lot of current for a short time. Can it handle, for example, the 200% overload of a 150A Megafuse for the 3 1/2 seconds required before the fuse blows? Probably. I certainly feel more confident about it with it being a ~7 gauge wire. In fact so much so that I don't think it's worth doing the experiment I proposed because I'm willing to bet on the fuse blowing.

It's also worth keeping in mind the chances of the failure scenario we are talking about, where the white wire supplying 12v to a bunch of fused circuits shorts to ground somewhere along it's ~6-8ft path between the battery to the two fuse blocks. It certainly could happen, but I've never read a report of it here on Mud and suspect the chances are relatively low. So it's like you said Bill, the alterations we make can have consequences and folks just need to be aware of what they are and assess them from a safety perspective themselves. As for me, I think the idea we're talking about, running a larger 2 gauge wire fused at 150A from the battery to the alternator and disconnecting the "Main 2.0L" fusible link is a good one and is what I'm going to do when I do my install.