Replace wiring harness? Options

[Boothy]

Happy new year all!

In the middle of a ground-up on a 74. Car is pretty clean but looking at the wiring. Looks clean as well. No chafing etc. Replacing the relays and cleaning the board etc.

Is wiring ever too old? Don't want to go through all this only to have to tear it all out with the engine in the way etc.

Car was a summer car in VT so no exposure to salt air etc.

Thanks in advance!

[Superhawk996]

Rarely is a wiring harness beyond repair unless it has been dunked in water (especially salt water) for an extended period of time. The water wicks way up into the insulation by capillary action and destroys it with corrosion.

If the insulation is pliable and intact, the copper within will be OK.

Brittle insulation will crack and cause all sorts of gremlins. Repair or replace.

Wire insulation can be tested with a Megger if in doubt about its integrity. However, at 12v, automotive wiring isn't at high risk of arcing due to insulation breakdown.

Bad sections of harness can be repaired by splicing with proper gauge wire and proper termination techniques.

The important harnesses (alternator, ignition, and Fuel Injection) are available from Jeff Bowlsby.

https://bowlsby.net/914/WiringHarnesses/