WSENG Articles: How to Install a Digital Tachometer

Equipment Needed:

• Tachometer (e.g. Nordskog Mini-Digital Tachometer Part # NRD-M9004-RB)
• Tachometer Pod (e.g. New South Performance Audi Pod)

• Run switched power from 75X terminal (red wire)
• Run a ground wire from ground point located under dash (black wire)
• Run a colored wire (purple) from headlight fuse wire, located in the fuse panel, to tachometer to enable day/night viewiing
• Run a RPM signal wire from the car's dash/ECU to the tachometer
  • On the 1999 Audi A4, the signal wire is located behind the dash cluster (Blue Connector (T32), Connector Pin 11, Green with Blue Strip wire)
• Remove Dash Cluster by following the following steps
  • Remove steering column cover by pull the cover straight towards the driver
  • Lower steering column to mid-to-low location
• Remove two securing screws and pull the instrument cluster forwards to access the connectors

  

• Disconnect blue connector by pulling/swinging the purple connector
• Cut off securing ziptie to release the cable bundle
• Locate the RPM signal wire.  You may also want to seperate the blue connector to verify the wire is located at pin 11.
• Use a razor blade or X-acto knife to cut around the circumference of the RPM signal wire.
• Pull back insulation with finger tips
• Solder your signal wire from the tachometer, and wrap with electrical tape

• Secure cable bundle with new zip tie
• Installation is the opposite of removal

Personal Installation Details:

I decided to install a switch in the back of the pod to allow me to turn the digital tachometer on or off as I desired.  I figured for the standard driving the display may become overly distracting.

Wiring Schematic

Red Wire -75X switched voltage source to Tachometer power switch. 

Red Wire #2 - Power wire from switch to tachometer power input

Black Ground - Ground wire to tachometer

Green Wire - Tachometer signal from RPM signal line behind dash

Purple wire - Headlight dimming wire