I am in the (hopefully) last stages of assembling my ‘72 914 and I’m hoping to install a stereo.

There are two mystery wires coming out of the hole where the stereo would be, although they do not appear to be the negative and positive wires (although I didn’t check if they independently have power to them). Any idea what they might be?

Backstory: I bought this 914 disassembled by a previous owner and I’m new to 914s, so it’s been a journey...

Can’t tell in the photo. What color are they?

It isn't for a stereo because those are not built in to the harness. Stereos had a separate harness. The brown wire is a ground. My guess is it is for the fan controls. There should be a tab on the slider mechanism to connect to ground. Can't tell what color the other wire is.

Check the wiring diagram for the fresh air heater control slider.

Thanks all, I’ll do just that!

Probably yellow. Yellow morphs to brown after 50 years. Peel back that insulation a tad to reveal the color.

Ha! I will totally peel back the wires to see what colors they were originally.

I did a little more digging into this last night and the smaller wire is brown with a white line, and it has 12 V to it with the ignition on.

The larger "brown" wire does not have any voltage. I don't think it's a ground wire either, because when I connect the two wires through a multimeter, I don't see any voltage.

FWIW, the fresh air fan works, so it's hooked up to something. And to make matters more confusing, there are similar wires (larger gauge brown, smaller gauge brown and white) in the harness as well that ARE hooked up to the fresh air controls. You can somewhat see them in the picture below.

Click to view attachment

only brown/white wire I see on schematic are: Parking brake contact , Brake warning Light, Parking brake contact in-line diode, Steering column switch to horn relay and Right side door switch (push button) FWIW

I wonder if the brown wire with white tracer is for the seat belt warning light.

I don't have a schematic handy but that would make sense. Brown with white tracer means a switched ground.

Not sure with a '72 model year 914 but on both of my 1974s, brown with white tracer wires are connected to the door contact switches on each side, meeting at the tunnel and going to the under passenger seat door open buzzer relay from which a single brown/white tracer wire heads up to the interior cabin light. My recollection is fuzzy but earlier models had a different system for the door contact switches in each side's door jamb. I think they were hot which is what the red/white wire might be. This brown/white wire appears to be too short to reach over to the passenger front door jamb.

That's right. For factory wiring, solid brown is a ground and brown with white tracer is a switched ground. You are right, door switches, brake lever contact, interior light, etc. all have brown with white tracer because those are switched grounds meaning that the ground circuit isn't completed until a switch makes contact. If you test the voltage on one of those wires upstream of the first switch in the circuit, it is going to read hot because you are completing the ground circuit with your meter or test light. If you test on the other side of an open switch, you will get nothing.

The interior light is a good demo because it has both a brown and brwn/white wire attached. One position on the light switch closes contact to the solid brown ground connector and the light comes on. The opposite position closes contact to the switched ground but the ground circuit isn't completed until you open a door and close a contact on a door switch.

This all may be interesting for understanding the theory behind the car wiring, but doesn't help with what that particular wire does. It also assumes a PO hasn't gotten creative with borrowing and splicing wire.