Installing a complete new wiring harness is a two-weekend job if you plan it correctly and a two-month nightmare if you don't.

Plan first: photograph every connector location before removal. Label every wire as you remove it. Remove the old harness as a single unit if possible — it shows you the routing that the factory used, which is there for a reason.

Install the new harness before connecting anything. Route it exactly as the factory routed it. Use the same clip locations. Only when the harness is fully routed and secured should you begin making connections, starting with the major power feeds and grounds.

Grounds are the most commonly under-appreciated part of the job. Engine ground, body-to-frame ground, and separate grounds for accessories. A single poor ground causes more intermittent electrical problems than any other single factor.