Electrical wiring

[JimT]

So I've been working on rehabbing my tractors electrical system. Thanks to all the great information on this forum. Right now I have 2 specific questions.

1: On many of the wiring harnesses the plastic wire loom is starting to fall apart. Brittle, cracking, even crumbling. Is it a better investment of my time and money to replace all the protective loom or just bite the bullet and replace the entire harnesses? I haven't found any actual bad connections or wires, yet. But the truck is almost 9 years old with 535,000 miles and if I have to remove the harnesses to properly fix them I'm thinking it might be a better investment to just replace them. Thoughts? Opinions? Usually if there's a question as to the future reliability of something I err on the side of caution and replace it, but at $2k for the 3 harnesses going to the ECM, it's not a trivial cost.

2: What particular products to people recommend for sealing/protecting exposed connections like battery/starter/alternator posts/terminals, ground locations, etc... I'm looking for actual brands/products that I can look up and compare. I've invested in new 4/0 cabling for all the major connections and I want to keep them in the best condition possible. Especially since I live in the Northeast and travel through the great road salt state, NY.