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titan3c
Samba Member
Joined: February 16, 2012
Posts: 568
Location: Coweta, Oklahoma
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 Posted: Thu Jul 16, 2015 5:42 am Post subject: Computer diagnostic unit |
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| What significance is the computer diagnostic unit? I know when the car was new it was handy in detecting problems, but I think that's a thing of the past. So does it still play a part in the function of the engine or can it be eliminated? I guess mine is still connected, but not sure. |
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Lars S
Samba Member
Joined: October 04, 2007
Posts: 786
Location: Sweden
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| Posted: Thu Jul 16, 2015 10:32 pm Post subject: |
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The VW diagnosis system on early/mid '70s cars is a plug in the cars engine compartment to which a number of wires are connected from factory. The wires comes from battery, ignition, starter motor etc. At the VW workshop the dealers diagnosis "computer" was connected to the plug and by reading voltages etc a printed protocol of the cars "health" could be issued.
The extra wires for the diagnosis system does not play any role in the function of the car and there is no "communication" to the cars Electronic Control Unit (if the car has EFI).
More info:
http://www.nls.net/mp/volks/htm/plug.htm
Computer to the left:
Lars S
_________________
Porsche 914 -72, Bahia Red daily driver 
VW411 2-d -70, White, sold 
VW412 4-d, -73, Gold Metallic, daily driver
Suzuki T500, -69, Candy Gold, sold
Suzuki K50, -77, Black, daily driver
BMW R69S -69, White, sold
Husqvarna 118cc, -47, Black, Sold |
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titan3c
Samba Member
Joined: February 16, 2012
Posts: 568
Location: Coweta, Oklahoma
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| Posted: Fri Jul 17, 2015 3:32 am Post subject: diagnostic computer |
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| Ok, Thank you. You answered my question. It has nothing to do with the operation with the function of the engine. I've had this car since new, and I remembered that the computer was used to diagnosis certain problems. But, I didn't know all the specifics you showed me here. Another question comes to mind. Does it have anything to do with the gas heater? Bob |
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Lars S
Samba Member
Joined: October 04, 2007
Posts: 786
Location: Sweden
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| Posted: Fri Jul 17, 2015 4:05 am Post subject: |
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No it has nothing to do with the heater function.
What car do you have?
Lars S
_________________
Porsche 914 -72, Bahia Red daily driver
VW411 2-d -70, White, sold
VW412 4-d, -73, Gold Metallic, daily driver
Suzuki T500, -69, Candy Gold, sold
Suzuki K50, -77, Black, daily driver
BMW R69S -69, White, sold
Husqvarna 118cc, -47, Black, Sold |
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titan3c
Samba Member
Joined: February 16, 2012
Posts: 568
Location: Coweta, Oklahoma
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| Posted: Fri Jul 17, 2015 1:14 pm Post subject: diagnostic computer |
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| Mine is a 71 411 4 door sedan. I'm the original and only owner. The only time the car has been out of my possession was when my daughter took it to college. I'm considering pulling the engine and transmission just to inspect, and replace old stuff. It still has most of the original stuff, but I think hoses, etc should be changed. I know the fuel lines are hard as steel, and that's no good. The car has 127,000 miles on it. I've been getting a lot of good information and help from Ray Greenwood on this car, and I'm pleased to find someone else who also has great knowledge of these cars. Thank you so much. Bob |
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KTPhil 
Samba Member
Joined: April 06, 2006
Posts: 34022
Location: Conejo Valley, CA
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| Posted: Sun Jul 19, 2015 8:59 pm Post subject: |
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Fun reading:
http://www.thesamba.com/vw/archives/manuals/dlt_computerdiagnosis.php
http://www.thesamba.com/vw/forum/viewtopic.php?t=256918
I have the dealer sign that hung over the station in the flyer/ad below:
You got a coupon book to record the results, and I believe one or two free diagnoses while under warranty.
The idea was to sell it as a way to save money by only repairing what needed it, not everything on a list. It also had a few nifty tricks, like doing an "electronic engine compression test" by analyzing voltage stop while cranking; it correlated compression in PSI to voltage drop at that point in the engine rotation while it was in the compression stroke for a given cylinder. |
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Lars S
Samba Member
Joined: October 04, 2007
Posts: 786
Location: Sweden
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| Posted: Mon Jul 20, 2015 12:16 am Post subject: |
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Wery intresting reading KTPhil!
Amazing what they could achive the old analogue way...well the computer was digital but most data was from measuring different voltages etc...
Lars S
_________________
Porsche 914 -72, Bahia Red daily driver
VW411 2-d -70, White, sold
VW412 4-d, -73, Gold Metallic, daily driver
Suzuki T500, -69, Candy Gold, sold
Suzuki K50, -77, Black, daily driver
BMW R69S -69, White, sold
Husqvarna 118cc, -47, Black, Sold |
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