MYSTERY Knob! Who Can Name It?
 

We're looking at a '72 (Edit: Convertible) with all your power options and A/C. I have little idea what this knob and these wires could be for. The radio doesn't work, and I have a feeling these may all be the reason why? Only other things in the area that appear inoperable are the center console gauges. Likewise, I found a mystery red wire with electrical tape that was threaded through and dangling by the shifter knob, but I think that's unrelated.


Here's the Knob in question. He refuses to talk! Give 'em hell, boys!

https://cimg2.ibsrv.net/gimg/www.cor...a336e95197.jpg


Flip side of the panel (Driver's side center console). Two obvious wire connection points...

https://cimg5.ibsrv.net/gimg/www.cor...11464fcc90.jpg


Local area busted wire. Not sure if related since the short end wouldn't reach the knob, and there is a 3rd wire tear on the opposite side.

https://cimg4.ibsrv.net/gimg/www.cor...4b18fd7b94.jpg


Passenger side broken wire for reference. Long enough to reach driver side of console.

https://cimg6.ibsrv.net/gimg/www.cor...c05933a559.jpg

Any ideas or guesses would be greatly appreciated. I'm hoping it's something I can fix up myself with my little car/wiring knowledge.

I think bubba was there

That was the factory placement for a rear defroster switch.
Have to see if defroster unit is still there.
Check under rear window behind drivers side seat.
Marshal

MYSTERY Knob! Who Can Name It?
 

looks like a potentiometer... for volume control, possibly for a line to a powered sub woofer?... who knows. Dig up the previous owner and ask them with a Ouija board.

I haven't considered that. This a convertible though; Would that still apply since it's a soft top?

Hi and welcome!
Not 100% sure about the wire in the third picture but if it's brown it might attach to the parking brake switch, does the dash 'brake' light go on when you pull up on the parking brake?

For the center gauges is the fuse good?

Here's a schematic, it's good except the direction of rotation for the distributor should be clockwise.
http://www.vetteprojects.com/bmv/mis...tte%201972.pdf

Regards, Pete.

We'll find him eventually...
https://cimg1.ibsrv.net/gimg/www.cor...9daf580fcc.jpg

Seriously though, what? haha

Thank you, Pete, I'll take a look. The parking break doesn't do anything at the moment, including brake! :lol:

I'm not use to these tube-shaped fuses, so I'm unclear on how to check their quality. I did just get a whole replacement set in the mail... I'm thinking about just swapping them all out. hahaha

So when you say dig up... :lol:
But I think you might be right. Or at least that's what Google Images thinks.

It looks like in the 3rd and 4th picture the wire has clear insulation those look like wires for the rear speaker. Hope you can figure things out, I have a wiring problem I have not been to find the problem yet, guess I will keep looking. Good luck.
Larry

Just replaced the gauge fuse! It was all red and nasty inside! After replacing it (accidentally shattering the old one trying to get it out), I saw instant feedback in my battery and oil gauges. Parking brake light works too. I'll have to take her for a spin and hope the gas and water temp work as well. Thank you! I know gauges are kind of a simple thing to check, but the focused answer geared me in the right direction. :yesnod:

That's a odd switch for Bubba to use I would think it would be a plastic toggle.

I kind of think it was a visit from bubba and used for something different.

If you look at the AIM pages you'll see the rear defroster switch had screws that held it in place. (none shown in the op's picture)... even if it was replaced there would still be the extra holes.

https://pbs.twimg.com/media/CQMpir_WsAEIpZj.png:large

The wire is speaker wire, and the knob was probably Bubba's fader.

As others have identified the 'mystery knob' is a potentiometer and was generally used as a fader to balance rear speakers.

Here's a diagram of how it should be wired. The more resistance dialed in made for less volume out the speaker.

Thank you all! Looks like you're onto something. And I think I'm starting to grasp who Bubba is. I would love to get that radio working; I suppose I just have to start tracing which wires need to be connected where...?


...To be completely honest I don't even know where the dang speakers are on this car. haha

The add-on rear speakers have likely been removed...which is why the speaker wires have been cut up front. Nice to have those wires in-place, though; you may want to reuse them. That 'fader' control didn't have enough current capacity to do its job...so it fried.

I agree. Looks like speaker wire if the wires in the pic were ever conected to it. Some type of homegrown sound system.

Hi GF,
I too am thinking 'fader switch'.
And yes, convertibles could have the rear defroster option too as the drawing Willcox posted illustrates.
Regards,
Alan

It looks like an ATR device. I wouldn't recommend connecting it.