linderpat

On the "W" block of the CE panel (78, manual), there is a lone tab, and no connector plugs into it from the front. When I pulled the panel for r&r, there was a lone blue/black wire in the back, unattached and just tucked in back there. It seems like it should be plugged into that lone tab on the W block. Does anyone know what this is for? Pics below.

SharkSkin

Ed, that tab is absolutely critical, which is why it's labeled "Not Used" in the tech specs book.

It's on the wiring diagram, sheet VII -- that tab goes to ground when there is no oil pressure. Not sure why they put it there.

linderpat

Thanks Dave - what got me wondering was looking at the pictures on your excellent site (I'm doing the fuse panel r&r, following along with your tremendous tutorial resource!).
Anyay - looking at your pics, it looked like that wire was plugged in at the end of the panel - I couldn't tell where exactly, so I was guessing the W block with that lone tab. What is the wire for? (I'll pull the WDs - hopefully they are easier to trace thru than the 86 was!)

linderpat

anyone else have any thoughts on the stray wire? (blue/black stripe)

SharkSkin

Well, it took me a while to get around to:

1. Checking out my CE panel
2. Eyeballing the PDF wiring diagram
3. Breaking out one of my original hardcopy color wiring diagrams to be sure

I've come to a few different conclusions:

1. That blue & black wire is supposed to be connected to W1
2. There is a blue/black wire where the diagram indicates, P2 on the CE panel.
3. Here is yet another place the WSM wiring diagram is in error
4. It would be helpful if I were to post the color diagrams

Based on my car, I'd say that the loose wire should connect to W1. Ed, since you already have the battery disconnected and CE panel out, would you mind checking to see if W1 and P2 are in fact connected internally on the CE? Also check to see whether the wires on the harness, the loose one and the one at P2, both have continuity to pin 2 on the 14-pin connector?

When I first thought of posting the color diagrams some time back, it was looking like an expensive proposition. Now I think I have a practical way to do it, so it's on the to-do list.

linderpat

Hmm. I already buttoned it up, but before I did, I looked to see where the lone wire went in the back of the board - it did go over towards P, but not sure if it went to 2. (I can't confirm the P block either, but it was very near there). The wire stayed low. Maybe Alan will have some input? I'll look at my WSM wire diagrams tonight.

Alan

So acording to the diagrams P2 goes to the oil pressure sender and connects to both G2 (dashboard) and (unused in the diagram) W2.

The representation in the diagram suggests there will be 2 wires crimped to one connector on the back of the panel - probably at P2 (I'd expect these wires to be the same colors).

So there is already a wire attached on the back of W2? (color?) The heat shrink on this doesn't look factory though the wire color does. Can't think where else the pressure switch O/P would need to go (except for aftermarket stuff).

Don't have a '78 for futher analysis...

Alan

linderpat

See my comments in red above, also, I may just hook it up and see what happens. after all, no brain to burn up or anything like that in this old bugger

linderpat

Here's the back of Dave's (Sharkskin's) panel from his site - it is pretty much just like mine (both from a 78) - look over at the W block, which is in the far right upper side of the pic - you can see one lone wire comming off that pin and running towards P (or some other block in that vicinity). Note the relative thin guage of the wire compared to many of the other wires on the back of the panel. You really can't see where it is going in this picture, as it is buried under all of the rest of the wires. But on mine, it stays low and runs a few blocks over, crimps in with another wire onto a pin there.

Alan

It would appear to be added just as a convenient monitoring point (which also explains the small guage). Porsche did the same for various years with the (61) alternator exciter wire and with some of the Alarm wires.

Before connecting it up I'd check for voltage on it (normally and also with ignition on).

Alan

SharkSkin

The connector on mine looks exactly the same. Same heat shrink, etc. It's been connected since I took delivery. I have quite a few pics of the CE panel in various stages of undress, but none that show any more detail about where that wire connects within the panel.

In addition to the checks above, it might be instructive to stall the car out and see if the oil pressure light comes on, one test with that wire connected and one with it disconnected.

linderpat

I reconnected it, and the car starts fine and I don't see anything wrong.

SharkSkin

I guess we'll just call it the "Mystery wire". Next time I have the battery disconnected I'll dig in and see what I can find, but I have a lot going on -- it may be a while.