A mysterious Wire and Box in the Engine Compartment

[Spanky]

I've found a cable clamped to the #1 spark plug wire about 2 inches above the distributor. The cable contains 2 wires + a ground wire and it goes to a mysterious plastic box mounted to the ceiling of the engine compartment. There is another cable containing many wires also running to this plastic box from I know not where.



These items were not on my other '73 THING built in Aug 1973.

I have pictures of these two items, the clamped cable and the box but I cannot figure how to attach them to this post.

Has anyone an idea what these items are for. Also I could use some picture posting instructions.

Thanks all!

Spanky
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1959 Renault Caravelle
1973 Citroen Maseratti SM
1974 Chevy Malibu Wagon
1979 Vespa Scooters (2), 1981 BMW R65
'73 Thingy.

[Fun 181]

From a post several days ago about how to upload pics...

http://www.thesamba.com/vw/forum/viewtopic.php?t=6

I always use the Samba Gallery to post my pics. Very easy to use.
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[Ian Epperson]

http://www.nls.net/mp/volks/htm/plug.htm

It's a diagnostic port for a system that's long since gone. All those connections go to several points in the engine bay, and it adds a significant complexity to the rear wiring harness. I just got done removing the plug and all the extra wiring while redoing the harness. Much cleaner.

Note that the link points out that the plug has test points for the turn signals and brake lights. I think this wasn't just for testing the wiring, it probably triggered the lights so the tech could verify that the bulbs were working.

[Spanky]

Yes it appears that this is indeed the diagnostic plug. I found a hinged "cap" on the bottom of the plug, pulled it open and was greeted by about a teaspoonful of grey powdered corrosion.
Bet that cap hasn't been opened in 34 years

I take it that this feature is now worthless?

Spanks
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1959 Renault Caravelle
1973 Citroen Maseratti SM
1974 Chevy Malibu Wagon
1979 Vespa Scooters (2), 1981 BMW R65
'73 Thingy.

[KTPhil]

If you know what it is wired to you can use it for some diagnostic purposes. It's just an easier way to get access to some connections and signals. It was a timesaver for the dealers who were coping with rising labor rates that made the VW less competitive for service cost. It had an interesting pseudo compression test mode that measured the relative strength of each cylinder by monitoring starter voltage drop (I think), but you can't do that manually. It may be thst after all these years the extra wires and connectors are more of a reliability problem!

[nemobuscaptain]

Does anyone have a picture of this and location of the wires? There is only one innthe gallery and it isnt helpful. Looks like a Type 4 bus engine hatch. Keep hearing it is in the engine compartment but my wires seem to disappear toward the front.

Im doing an alternator conversion and I found at least two wires or this diagnostic test connector. Im wondering where the go. Id started to cut them.and.pull them. However it occured to me that I might want to leave the front to rear wires if they are already in the harness ie perhaps a wire for a cyl head or engine oil temp gauge.
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Hoover Sermons: https://www.vwsage.com/images/vwsage/Bob%20Hoovers%20Sermons.pdf

[Semper_Dad]

There are several downloadable "current flow" diagrams and schematics for 181 in the electrical technical sections of this website. Anything with an orange dot corresponds to a pin on the test connector. The color coding for the wires also correlate. There are no test points or diagnostic wiring that that lead forward via the main harness. I always though it would be neat to fabricate a dongle in order to access these test points. You could hook up a tach, remote start the car. and other stuff. However, my recent engine bay fire obliterated the plug and all of it's associated wiring making that plan moot.

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Walküre Restoration Thread: https://www.thesamba.com/vw/forum/viewtopic.php?t=737492

[mondshine]

Nemo-
First, be careful about cutting those wires; especially 15, 30, 50. You don't want any loose uninsulated wires dangling in the breeze.

I don't believe that there are any wires associated with the diagnostic system that run fully "back to front".
In any event, you would be farther ahead to fabricate your own harness for gauges, etc. That way, you could select the wire gauge and colors that conform to DIN standards, or at least "make sense" so that when you look at it in the future, it won't be a mystery.
I have done this on a couple of cars, and I always document what I have done for future reference (so I can remember what I've done).

A good tip is to first make the "harness" out of cheap string. You can get all of the lengths, breakouts, etc., exactly right before you start cutting any wire. This will prevent costly mistakes.
So have fun with it, and good luck.

[vwlowbug]

Correct on the wires, they don't go to the front. You can remove the main Batt + feed to that plug on the starter motor for example.
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-2008 Caravelle Executive Sportline TDI
-2005 Touran TDI
-1972 181
-1968 Custom Bug
-1967 Splitscreen Kombi 11 Window
-1955 Barndoor Standard