I found this wire behind the radio in my 1974 XKE OTS with a 4 speed. Any idea where it goes?

 

Just guessing but perhaps used for the rear window defogger on the coupes, so not used on the OTS.

 

Here is my guess. The label on the radio says negative polarity which synonymous with positive ground. But at his stage, all etypes were negative ground. Perhaps your radio is a retrofit which would have needed some rewiring. The wire may be 12v from the ignition switch accessory position used to power the original radio and cannot be used now. Alternately, it may the original ground wire which also cannot be used. If this guess is true, the chassis of your radio may be 12v and needs to be isolated from ground. You should have this checked in case it was not done properly.

 

it is hard to determine what that wire is without knowing a few things.
What color is the wire? Have you checked it with a voltmeter to determine if it has power to it with Ignition Off, on, on accessory?
Bill.

 

I stopped worrying about disconnected wires in that rats nest back there. There are lots of wires that are intended for alternate configurations. I think the rear window defog is a good bet, I know its a 16 or 14 gauge black wire.
But, more importantly, what does "OTS" stand for? I have a '74 series 3 roadster, but I don't think I've seen that designation.

 

OTS = Open Two Seater. Roadster.