Diagnostic Plug

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broady_6
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Diagnostic Plug

Post by broady_6 » 11th November 2018 - 10:34am

Im not desperate for one, Just curious, does anyone have the diagnostic plug for one of these? I assume its the same thing across all the VW's of the period?

(started as a wanted ad and got more interesting so mirrored to the workshop)
The sultan of swing

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eagle
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Re: Diagnostic Plug

Post by eagle » 11th November 2018 - 7:23pm

I've got a couple of looms. I can't remember if they have them but I could have a look.

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broady_6
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Re: Diagnostic Plug

Post by broady_6 » 11th November 2018 - 9:33pm

If they are looms from the car, that's the socket. The plug is on the computer which got plugged into the car
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937carrera
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Re: Diagnostic Plug

Post by 937carrera » 12th November 2018 - 11:15am

Are you planning on making your own diagnostic computer :)

A couple of guys are using arduino to create GPS based trip computers for the T25's
David
1974 412LS Variant
1973 412LE 4 door Fastback / Saloon

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purplepeter
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Re: Diagnostic Plug

Post by purplepeter » 12th November 2018 - 12:12pm

I think I've only ever seen 1 for sale, about 10 years ago (around £75)
There's a bit of explanation here http://www.nls.net/mp/volks/htm/plug.htm
But I have it in mind that somewhere I might have a fuller explanation

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broady_6
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Re: Diagnostic Plug

Post by broady_6 » 12th November 2018 - 10:58pm

937carrera wrote:
12th November 2018 - 11:15am
Are you planning on making your own diagnostic computer :)

A couple of guys are using arduino to create GPS based trip computers for the T25's
I dont really know what im planning, I just wanted one for the novelty. Could have been an easy jumpstart point if ever required.
purplepeter wrote:
12th November 2018 - 12:12pm
I think I've only ever seen 1 for sale, about 10 years ago (around £75)
There's a bit of explanation here http://www.nls.net/mp/volks/htm/plug.htm
But I have it in mind that somewhere I might have a fuller explanation
Wow, maybe I don't want one then, I was prepared to spend £10-£20 haha. I use that link to rewire mine as I wanted to know what half the pins did and see what I could do with it. Id be interested if you do come up with more info. Have you run out of coffee yet?

One that particularly interests me is how they monitored compression, I assume that was something to do with the FI set up
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937carrera
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Re: Diagnostic Plug

Post by 937carrera » 12th November 2018 - 11:08pm

broady_6 wrote:
12th November 2018 - 10:58pm
One that particularly interests me is how they monitored compression, I assume that was something to do with the FI set up
Yeah, that was quite interesting, though I don't see why it should only be used for FI engines.

Can a man of your abilities do the maths / alogorithm to convert battery voltage, cranking voltage, expected frictional losses, starter motor efficiency and engine rotation speed to a compression value by cylinder in bar ?

I can see the concept, nowhere near having the engineering knowledge to work it out :lol:
David
1974 412LS Variant
1973 412LE 4 door Fastback / Saloon

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937carrera
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Re: Diagnostic Plug

Post by 937carrera » 12th November 2018 - 11:44pm

David
1974 412LS Variant
1973 412LE 4 door Fastback / Saloon

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broady_6
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Re: Diagnostic Plug

Post by broady_6 » 13th November 2018 - 7:22pm

937carrera wrote:
12th November 2018 - 11:08pm
broady_6 wrote:
12th November 2018 - 10:58pm
One that particularly interests me is how they monitored compression, I assume that was something to do with the FI set up
Yeah, that was quite interesting, though I don't see why it should only be used for FI engines.

Can a man of your abilities do the maths / alogorithm to convert battery voltage, cranking voltage, expected frictional losses, starter motor efficiency and engine rotation speed to a compression value by cylinder in bar ?

I can see the concept, nowhere near having the engineering knowledge to work it out :lol:
I hadn't even thought that far into it. I just assumed FI engines because they would have some sort of air metering system on the intake, and if compression is good (ie valve and ring seal is good) you would getting more "suck" in the cylinder increasing the air flow in the intake.

I assume you are thinking along the line of "energy required to turn the engine over during the starting phase?"

Ta for the links, I shall have a read of those this evening. I seem to have started a decent topic here, just in the wrong section :lol:
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937carrera
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Re: Diagnostic Plug

Post by 937carrera » 13th November 2018 - 7:41pm

Yep, I am thinking about energy required to crank = work required to compress air.

I you were a mod you could just move the topic into another section and then post another wanted ad. O hang on ... :)
David
1974 412LS Variant
1973 412LE 4 door Fastback / Saloon


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broady_6
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Re: Diagnostic Plug

Post by broady_6 » 15th November 2018 - 7:52pm

I have now, thats ace! And Mr 937 was bang on!
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broady_6
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Re: Diagnostic Plug

Post by broady_6 » 16th November 2018 - 10:12pm

Edit, i now feel very foolish, of course id seen that, it was the link mr purple posted earlier in the thread, its just that i cant remember more than 30 seconds at a time :lol: :lol:
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Editor
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Re: Diagnostic Plug

Post by Editor » 19th November 2018 - 1:28pm

I took my old Beetle into the dealership for a diagnosis around the time they had the diagnosis system. Obviously they couldn't do the whole job, and reported faults that weren't there (like front toe-in being zero, which was correct for radials). Sadly they did not report the rear linings being down to the mesh backing, which I discovered the next day when both handbrake cables broke due to the quadrant cutting into them. Since rear hub removal was needed, I returned the next day, and left the evidence. They also replaced the weeping wheel cylinders with the wrong (later) ones. After that I started to do my own maintenance!
Dave.

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