VEMS Community Forum

Technical => Wiring & Sensors => Topic started by: Mark0 on July 19, 2014, 05:49:52 pm

Title: VEMS tacho wire
Post by: Mark0 on July 19, 2014, 05:49:52 pm

Hello, it's possible to make original S4 2001 tacho work with VEMS ? I have wire from ECU to external tachometer (from AutoGauge) i didn't tested because engine removed... The problem is that on VDO cluster don't know which one is for tachometer. And in my opinion it's not just connecting wires, am i right ? VemsTune showing revs, but original tachometer not. A bit weird, than only speed on cluster working...

Title: Re: VEMS tacho wire
Post by: smurfinator on July 20, 2014, 03:40:57 am

I got my VEMS to work with OEM 1993 Audi 90q tach by looking up the Bentley wiring schematic.  It will tell you the color of the input wire and the color/pins of the connector on the gauge cluster board.  It my case it was the green with blue stipe to the 26 pin yellow connector.  I clipped that and wired in the VEMS stepper output to the cluster board end of the wire (duh).

I used S259 #3 as tach output but I also had to activate s259 channel #7 (as water pump) at -40degC because you need to power up the s250 chip.  Apparently tach output will no do that by itself :P

I used staight output with no diode and a starting tach divider of 12.  Now it's at 22 with a v8 to show correct RPMS as told by the VEMS dashboard.