petrol rev counter - green route?

[CovKid]

Picked up the green at the clocks ok but I cannot find other end in engine bay. There is a green on neg side of coil but this goes to ignition amplifier so I can rule that out.

Now, assuming VW tended to stick to same loom (more or less), I wager that the wire still runs to the back but just unconnected on those without the counter. Its certainly at dash end. Any idea where this green wire could be located in engine bay area?

[silverbullet]

I think that the looms were specific but not definite. If you have a green at the dash then it must terminate at the 7-pin plug.
A tacho gets its impulse from the LT side if the coil, so pick it up there.

[CovKid]

Just had a closer look at 7-pin. Nothing there I felt fitted the bill. Green/black only (indicator circuit) so I'll have to run one by the looks of it. Thanks fella.

Will see if I can follow green at dash while I'm at it. Perhaps its only a partial tach loom on mine.

[silverbullet]

My 1990 small window SA is similar (basic speedo & clock dash, fog lamp wiring stops at junction box)
I need to slide under and take a few pics of the transmission so will try and have a look.

[silverbullet]

Reading it in reverse direction as it were:
Green from dash panel end is track 1 on wiring diagrams. Feeds tacho and coil via T7a (round connector in junction box) pin 5
There appears to be a red/black jumper on the back of the relay board D26 to D19, then green to feed terminal 1 on the coil, looping to pin 1 on the TCI unit.

[CovKid]

Looks as though mine lacks this at engine end then so I'll pick up a length of twin-core at Wilco in the morning and use one strand for alternator trigger wire (which needs replacing anyway) and the other for tacho feed. Not ideal but it'll do the job and easy enough to route underneath encased like that.

I'll nose the wiring diagram this evening just in case I'm not following the tacho path properly. Thanks chap.

[itchyfeet]

Tacho green goes via the fusebox on a late van also and can be seen on one of the round connectors in the black box, earlier vans without the buzzer of doom didn't have the wire as standard afaik, it was added for the buzzer to know it's above 2000rpm.

[silverbullet]

That would explain the lack of a green wire.

[CovKid]

I wonder what the green wire at dash is then. Mines an 85 caravelle with speedo and analogue clock. Tacho is now installed but dead without the feed. Looks like I'll have to disregard that green entirely (wherever it goes) and just run a new line to coil negative.

[itchyfeet]

Change over year I think, maybe a mix of looms?, worth checking the black box circular connectors, if it's in the loom it goes via there, from there it joins to coil with the other green on late van.

E D I T, thats what you mean by 7 pin plug isn't it?

[CovKid]

Aye. I think you're right on changeover year. Bit 'mis-leading' that green wire at dash (excuse the pun). Still it may help anyone in future trying to wire one in.

[silverbullet]

Green wire at dash may only go as far as the relay board.
Is yours a single pressure switch engine?

[CovKid]

Yup. By the looks of it it never even reaches the back. Have checked every colour in back box. In daylight I'll see if its possible to determine just how far that green wire actually goes but I have a feeling it only exists at dash.

[CovKid]

Yay!! I have a rev counter (OEM one) where the analogue clock was. I had to run a new cable. Bought 8 metres and had 1/2 metre left over. Amazing how long the run is if you have to route it underneath. Heard folk suggest its as little as 4 metres - maybe as the crow flies but not if you want it clipped up tidy and to come up behind the dash.

[itchyfeet]