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Roon · Joined: 25 Jun 2007 Posts: 13 Location: Sydney, AUSTRALIA

I've tried searching the forum but haven't found what I'm looking for (yet). My '81 Turbo (AUS) runs fine, however the tach just stopped working. Should the needle move when the ignition is switched on? I assume the green wire on the back of the Tach is the "pulse" signal. I can trace this back to the fuel pump relay, however I can't trace the green wire that goes from the relay board, through the firewall and into the engine bay harness. Where does the actual tach signal originate?

Thanks

Cameron

Smoothie · Posted: Sat May 03, 2008 11:31 pm Post subject:

The wiring diagrams show it. Find the tach and trace the path backwards. -And you should find the signal passes through a couple of connectors on the 2nd page of the diagrams. One of those connectors also involves the alarm system..
_________________
"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

Roon · Joined: 25 Jun 2007 Posts: 13 Location: Sydney, AUSTRALIA

that's my problem, I don't belive my AUS 932 has an alarm system or if it does where does it live/what does it look like? I bought this car from a young 'un who thought a 147Kw stereo is the most important feature of a vehicle and as such the relay board is currently lying in the passenger footwell (RHD) while I cut out the myriad of surplus wires to get the harness back to something that I can fathom....and no, I haven't cut any of the original harness, just the obvious add on wires for the stereo/amp/speakers. The tacho was working then just quit one day whilst driving , so I'm not sure if the tach signal has been lost or whether the tach itself has gone, hence my question should the tach show any movement with just ignition on? I don't have access to any other 931s locally unless someone in Sydney wants to give me a call so we can meet up? Smoothie, I appreciate your input...Cameron

Smoothie · Posted: Sun May 04, 2008 5:17 pm Post subject:

Some clues to the presence of the factory alarm would be a key operated switch located below the small side-rear window ("quarter window") presumably on your drivers' side, rear of and roughly level with the door handle. -And the alarm horn should be in the cowl area below-behind the bottom of the windshield (at the left side (on my car)).
-But whether you have the alarm or not, connector "T1a" should be present, "near ac-compressor" (as noted on page 7 of the diagrams). The other involved connector is "T6a" (pole 3 of this connector is a green wire that goes to the tach) - it's a 6-pole connector "near fuse/relay board".
_________________
"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

Roon · Joined: 25 Jun 2007 Posts: 13 Location: Sydney, AUSTRALIA

After reading posts on Fuel Pump relays etc I came to understand that a 931 wouldn't even run without a tach signal and therefore assumed that the tach itself was faulty. My local VDO shop diagnosed the main IC had blown, they replaced it and I now have a tach again. I'm slowly working my way through understanding the plumbing and wiring on my car..its really running strong now that ALL the vacuum lines/connectors have been replaced whether they looked good or not, I can't reinforce how important it is to replace all the vacuum related rubber BEFORE trying to solve rough running, idle fluctuations etc. Thanks to this forum for your assistance, in particular Sir Smoothie..

Cheers from Down Under