Couple more questions for my 74

[Shark_13]

The horn fix was a success, thank you guys.

I am in the process of replacing both gas tanks & senders, due to the fuel gauge not working and I ran out of gas oops. The old senders both had very random, sporadic readings so they were due for replacement anyways.

New tanks are in, both senders tested prior to install into tank.

1 ohm empty and 90 ohms full , manually moving the floats.

Pulled the harness from the firewall connection. Blue wire is testing near empty, which is correct as that driver's tank is the one I just installed.
Tan with white stripe I believe is the passenger side sender. About 70 ohms , maybe 3/4 full tank?

Green wire to the fuel selector valve. That was working previously so all good.

Leaves a tan wire, seems to do an odd loop from firewall connector, through harness, back up frame rail, and back into harness going into truck.

I'm assuming this is going to the switch and/or gauge?



Maybe unrelated or maybe not, I found this plug disconnected just above the brake booster.

Anyone know what it might be for?

Thanks