Hi,
On my 70’ CS 350 the alternator is an externally regulated version but I don’t notice a ground wire in either the connector going to the horn relay and regulator or directly to battery. Is there supposed to be a ground for this model?

 

I think the ground is the connection of the unit to the firewall.

 

The ground is through the metal case to the metal bracket to the metal block.

 

The horn relay actually gets its ground from the steering wheel horn switch. The remainder of the connections are all pos 12v.