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Thu Sep 02, 2010 3:04 pm

Anybody know what the diagnostic computer actually checked or if there is a practical use for the plug when working on the car?

I'd love to have one of those computers. Just for the fun of it... :roll:

Thu Sep 02, 2010 3:08 pm

I just checked lights, timing. There were no computers in the car so there was no data logging.

Thu Sep 02, 2010 3:15 pm

Glenn wrote: I just checked lights, timing.

It checked the battery too (didn't you listen to Buzz?)

I assumed no data logging. I puzzled what you might check past voltage and current on a car where the only electronics are in the radio... (which mine never had)
I was curious if there was anything of value and I could see the potential for making use of the timing feature at very least.

Thu Sep 02, 2010 3:21 pm

Do a search...you'll find quite a few people who use the plug
Such as:

Posted: Wed Jun 02, 2010 1:02 pm Post subject:

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Speaking as someone who has just finishing restoring my engine compartment (including restoring the diagnostic harness)

THE THING IS ABSOLUTELY USEFUL.

As long as it hasn't been hacked up by thumb-fingered blingers more interested in appearance than functionality.

From my diag harness, I can crank the starter, close the ignition and start the car, check my dwell and rpm, performing stroboscopic timing (with a gun hooked up to the ring pulse transformer on the #1 wire) as well as check my generator output and battery charge.

All of this without even getting my hands greasy. So....useful? You betcha. With an intact diag system and a $7 multimeter and some jumpers, there isn't much in engine electricals that you can't diagnose.

But it can't be hacked up, and its connections do need to all be in place for it to be this useful. If you tune by instruments, rather than by ear, it is a brilliant piece of kit.

Now things like the 'light bulb' checks are a little silly. But lots of things it does are dead USEFUL.
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And here's some great information on the plug from Speedy Jim:
http://www.nls.net/mp/volks/htm/plug.htm

Thu Sep 02, 2010 3:29 pm

As I understand it, the attached computer could also check the relative compression of each cylinder based on the crankshaft position sensor & the voltage drop from the starter! Pretty darn engenius those German engineers were back in the day.

Thu Sep 02, 2010 3:50 pm

MrVWGuy wrote: Pretty darn engenius those German engineers were back in the day.

I'm an Electrical engineer in the aviation industry and I have to admit I believe modern technology has made us fat and lazy compared to previous generations. I think in past technical limitation force engineers to find more creative solutions and the lack of calculators and simulation software bred a stronger basic understanding of how things work.

Thu Sep 02, 2010 6:53 pm

Hiya Hank,

I had most of the components in the VW Diagnostic System. I sold those components a few years back.

The Diagnostic System would check about 70 items onboard the car. The actual number varied from year to year and model to model. Most of those 70 (or so) items checked were not input by the computer. Rather they were entered by a technician with a hand-held "paddle". By the way that paddle (it's blue) is visible in the commercial as Buzz walks over to the computer units.

It worked like this........after the car was plugged in a program card (made of plastic and you see this also in the commercial being read by the input reader) for a particular model was inserted into the computer. This card program directed the tests and set the standards for each model of car. As the computer did its monitoring jobs, the technician added his inputs. Those inputs were in the form of + and -. This was strictly a go, no-go kinda evaluation. This was very much a stone-age type computer. The printer would spit out a form listing the items checked and the results.

VW actually used this system as much for marketing (probably more - witness the commercial you linked) as for any sort of diagnostic work.

Thu Sep 02, 2010 7:09 pm

Bookwus wrote: VW actually used this system as much for marketing (probably more - witness the commercial you linked) as for any sort of diagnostic work. And I actually expected Buzz to say that the computer used to diagnose your bug was more powerful than the one in Apollo XI! :lol:

Thu Sep 02, 2010 8:16 pm

mnussbau wrote: Bookwus wrote: VW actually used this system as much for marketing (probably more - witness the commercial you linked) as for any sort of diagnostic work. And I actually expected Buzz to say that the computer used to diagnose your bug was more powerful than the one in Apollo XI! :lol:
:shock: :lol: :lol: :lol: :roll:

Thu Sep 02, 2010 8:32 pm

I use to work for VW recently let go and the new TDIs can tell you running compression with the glow plugs now that was cool to see. they computers in the new cars are crazy and to think it all started from 72 to 2011 cars and still going.

Thu Sep 02, 2010 9:20 pm

Does the computer make those cool beeping sound like in the end of the commercial? because that's the deal breaker for me.

Thu Sep 02, 2010 9:56 pm

You dont even need the computer. a decent multimeter can perform all the functions that the computer did.
http://www.thesamba.com/vw/archives/info/wiring/bug_72.jpg
If you look to the right it has all the pins numbered. if you look in the schematic the numbers are circled throughout it and tied into different places in the schematic. most of these are just test points (see if you have 12 volts) before i even knew i was staring at the reverse light fuse (didnt know it was next to the coil) i used the test point to determine that there was 0 voltage after the fuse.
As for all of those you dont even need a voltmeter you can use an elcheapo 12v bulb or lamp from radioshack.
the one that gets pricey trying to use is the inductive sensor on the plug wire as your meter has to be capable of measuring inductance, most of them dont.

Thu Sep 02, 2010 10:19 pm

some of the wiring can be useful. The battery check wire is pre ran though the firewall next to the main harness for installing a tach or other instruments, for your convenience.

The plug and everything else, not so much. Its almost easier to hook up a timing light or dwell meter without fiddling with the socket. You don't need wiring running everywhere that might carry current either. I have the socket and everything, but it isnt hacked so I'll remove it eventually.