Alternator wiring failures due to Sportsmobile splices

[moorefc]

This is for a 95 E250, but could be a common long term failure issue due to Sportsmobile battery isolator wiring design. Two failures in two alternator output splices! A couple years ago in the Badlands noticed alternator was not charging. It was about 100 deg and ended up driving 130miles after noticing this (all fans etc off). With a good starter battery that was pretty amazing, and when arriving in St Paul battery was 11.9v with engine running. Turned out to be a wiring short to ground on the starter battery to isolator leg. Sportsmobile cuts into the alternator B+ harness and runs that starter battery leg to the isolator. I couldn't find the picture of the very ugly splice, but Sportsmobile used 8ga wire to the isolator while the factory end to the battery is 6ga. This means the 6ga side of the splice was overspliced and about 50% of the strands were sheared at the splice! Looks like Sportsmobile used a 8ga crimp on the 6ga wire. This overcrimp eventually fatigued, additional strands failed, heated (offroad bouncing), melted insulation, and shorted against the frame, taking out the sense lead fuse wire. I replaced all that with new splice and 6ga wire to the isolator. (Longer story was the shop that I handed it to after I could not find fuseable link didn't find the harness short, but next offroading in Colorado a week later shorted again, and I found and fixed it).
Now, two years later on a trip to Baja noticed the alternator wasn't not charging. Limped into a autozone, finally found melted B+ alternator output wire just after alternator terminal (melted mess). It was so fused open there was no splice left! One can guess what happened. Splice was 6ga at the terminal, then 8ga to the isolator. After the first failure I wasn't smart enough to check the other side (of the spliced cabling) for the same issue, here it is, and sportsmobile used the original wire end at the alternator and added a splice to the downsized wire. This is just where the wire turns and absorbs engine movement/vibration. So 180K miles did it in.
So you may want to look at your wiring at those two splices, or if your system is no longer charging check for those cheezy splices....This was a disappointment because most of the rest of the van wiring has been great.
I did not report the first problem, but after the second....it is very poor practice to downsize ford factory wiring AT THE ALTERNATOR and splice to a different guage wire.
Otherwise the van has been pretty darn wonderful!

[carringb]

That's frustrating. I wonder why they just didn't use the factory isolator and RV wiring harness (there's factory sockets to plug into under the hood, under the dash, and in the B-pillar)?

Good find though. Glad to hear you didn't have to pay a shop to fix it.

[moorefc]

The first time there was a cost, however the reason for the post is I have worked on a couple 2000 ish Sportsmobiles and they appear to have the same wiring setup. Whether the downsized wire was used with the crimp problems is unknown. But the final indicator is the charging guage, followed by the speedometer and odometer going crazy when the voltage gets low enough. That got my attention the second time. Speedo read 60, then 0, then jumped to 85+. That gets your attention!

The isolator in all the cases I have seen is mounted on the front next to radiator riders side....Short run from the alternator.

Cheers