Voltage drop

[h20hamelan]

and the older copper is most likely of superior quality, over new.
the connections do take the abuse, also from vibration
every time a current is applied, there is (albeit minor) arching which leads to carbon deposits and loss
further, if you have chafing (not of the undies)

[Elan45]

My next try would be the ground (earth) in the boot, after all, its a freebie.

RL

[seniorchristo]

Problem solved.. I spent a few hours this morning adding a relay for the horn. Makes a big difference. Now the horn is LOUD ! I now understand grounding the horn directly with a relay, versus through the steering column is the way to go. However I'm still not sure iif my voltage drop is normal. Thanks for the help as always Chris

[alan.barker]

Maybe you still need to bypass Ignition Switch to prove if there is resistance.
Alan