67 Cutlass AM radio, stock...

There is a single blue wire, with female spade connector on side of 67 AM Delco radio. What's it for?

Rear speaker?

Someone told me I have to have a 'fader' for a rear speaker, but if it is something separate, I assume I don't have that either.

Already posted the radio isn't working, but need to find what the blue wire is, and if I've got to try to find a fader.

Thanks,

 

It is most likely for the rear speaker. In 72, the wire running to the rear speaker was blue. The negative side is chassis ground.

Not sure if the fader was separate in 67; but someone else will know for sure.