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Well the trip to the wrecking yard shed some light on the mystery. There was a late model 73 fastback with manual transmission. The ECU was a 021E with no potentiometer. We looked at some the guy had on the shelf and found a 021E with a potentiometer.and the potentiometer had a name in German, plus 5k. It confirmed for me that the potentiometer actually exists. When I got home I double checked my ECU part number and it is a 021E. The picture at http://www.geocities.com/MotorCity/Shop/4123/Potent.html is from a type-4 914, I know that because the farther I dug into the haystack (website) things migrated fully to the 914. It even had a link to a site in LA to rent the VW 1218 tester. I've been repairing and operating ships for 28+ years and every once in a while we run into problems similar to this. What we find is there are sometimes short runs of equipment manufacturing that takes place between one model and the new and improved model. The changes in the short run are so few and the actual numbers of units built is so small, that the differences never get documented. And to fix the equipment we reverse engineer it, fix the problem and document what we did. I think this could be part of the issue with some of the late 72 and the 73 type 3. I've taken a look at three 73 type-3 cars and all three engines were different in small ways, but all of them lacked EGR equipment that would probably indicate they were not built for sale in CA. I suspect to find out what the two wires (41/42) are for is to reverse engineer the system by cutting the cable bundle covering back and follow the wire and see were it ends. My gut feeling tell me it was probably part of the CA smog system the or the on car diagnostic system the car was built with. If it was part of the ECU the module would have to be grounded and the other two wires would attach to the potentiometer in order to make it adjustable. Tomorrow I may go take a look at a wrecking yard north of here that specializes in VW's, the yard I was at today was about a mile from the Mexico border and I don't speak any Spanish. The saga continues. Jim in San Diego ----- Original Message ----- From: "Russ Wolfe" <russella@prairieinet.net> To: "type3" <type3@vwtype3.org> Sent: Saturday, July 28, 2001 1:50 PM Subject: Re: [T3] Mystry wire > Subject: [T3] Mystry wire > > > > I am stumped. I have a 72 Squareback built in June 72 but the wiring > harness > > and FI match the diagrams for August 72 and later. There is a plug next to > > the pressure sensor with 2 wires numbered 41 and 42. they don't show in > any > > wiring diagrams I can find, including the Bentley manual. I think it may > be > > associated with my FI. A FI manual I have (plus additional book) indicate > > the August 72 (and later), plus 73 ECU 311-906-021E (black color code) > were > > built with a potentiometer on the ECU to adjust CO admissions. Sounded > like > > a great deal to me then I checked my ECU. The ECU has the correct PN (no > > black marking?) but no CO potentiometer on the outside. Since my car > seamed > > to be built during the gray area of a production year (model year shift), > I > > turned to the INTERNET found a good FI troubleshooting site > > http://www.estinc.com/porsche/djet.html and low and behold I found that > some > > of the late 72's were built with the potentiometer next to the pressure > > sensor (PN 311 > > 906 019). Here's the mystery I think my car was one of them, but was it? > If > > not what are those two wires for? For the electronically gifted there is > an > > excellent site for the ECU dissection > > http://members.rennlist.com/pbanders/ecu.htm (pictures and schematics). I > am > > off to look at some 72 and 73 type-3's at the local wrecking yard. I would > > be eternally grateful for any leads. > > I have never seen a T-3 with either potentiometer. The picture shown at: > http://www.geocities.com/MotorCity/Shop/4123/Potent.html is of a type-4. > Notice the fuel pressure regulator next to the intake runners. It is on the > wrong side for a T-3. > Those extra wires you have may not been connected in the ECU. > What is the number on your ECU? > > Russ Wolfe > russw@classicvw.org > http://www.classicvw.org/ > > ------------------------------------------------------------------- > Too much? Digest! mailto:type3-d-request@vwtype3.org Subj=subscribe >