Older Cars - No Speed Sensor (GAL) wire:
Posted by TS on 3/17/2005, 6:00 am, in reply to "TP 4773 and MBZ 300D Speed Sensor":
The speed sensor line in that car was to run the cruise and ABS systems. Neither activate at a slow enough speed to be useful to the Trafficpro. The Harman/Becker Parts dept has a Speed Sensor Adapter that installs in line on the speedometer cable at the trans or speedometer head. Wire it to power and ground and it generates the proper HALL Pulse based on the spinning of that cable.

"Traffic pro installation in 1990 C2 Porsche"
Posted by JPS on 3/6/2006, 9:13 pm
I am trying to install aa Traffic Pro into this car and I do not have a GAL wire. Is there another wire or way to get this done? Will the Traffic Pro work without it?
JPS

Posted by alpina22 on 3/8/2006, 9:36 am, in reply to "Traffic pro installation in 1990 C2 Porsche"
Your car has a speed signal
Easiest method is to locate the wire (red/white IIRC) from the HVAC control panel. Use a DIN radio removal tool to pull the HVAC panel and disconnect the two large connectors. This makes it easier to tap the speed signal wire. To confirm you have located the correct wire, pull the speedometer and find the red/white wire. Set your multi-metre to Ohms. It should register a 1 Ohm load. However, if you probe the red/white wire at speedo and HVAC at the same time, it'll ground the wire giving you a zero load.
Did this on a MY91 C4 and it worked 100%.

The 964 belonged to a friend. He was very pleased with the TP. I've installed them in several 993s and BMW M Coupes over the last year. As for your dilemma, get to the speed wire at the back of your HVAC panel. It's just a 10 minute process. Just get some 18-22 gauge wire taps (red) from Radio Shack and attach a [same gauge] wire from the speed signal wire to your TP, pin 1, socket A.