I am currently working on the firewall wiring harness on my 65 biscayne and have some problems with the factory wiring versus what my schematic shows.
First, I have extra wires for my windshield washer pump (one that comes through the plug on the fire wall (part of the harness) which I had labeled "WW Pump" (also shown on my schematic) so I know that is where it came from. I also have another 3-wire cable that comes through the firewall by itself and has two connectors on it for a total of 5-terminals that mates up perfectly with the washer pump.

Next I have a wire for my heater blower motor which goes to what looks like the horn relay in appearance except it sits atop my AC box on the passenger side firewall. Here, my schematic says it goes to the blower motor and thats it. What I have are several other wires going in several different directions. What is this "relay" looking thing and what are these other wires for?

I am short on time so I will get more specific if I get some response. Hopefully there are other classic '65 chevy (and others: imp, bel, caprice, and other yrs) that can help. Thanks all!!