thanks Ian, I did forget to mention the light to the gauge.


in the attached pictures you can see the red/white wire and the black ground for the light.
I had to source the light. Since it was plastic I needed the ground.

you can also see the 3 wires going through the hole in the speedo to the temperature gauge :
  -  red/white wire from loom to temp gauge light
  -  light green wire from "I" terminal on voltage stabilizer to temp gauge terminal
  -  green/blue wire from loom to temp gauge terminal

it was the green/blue wire which was too short to attached to the temp gauge so I had to source
a short green/blue wire with female/male spade connectors to bridge the gap.

hope this picture helps everyone.

Hi Roger, according to my factory w/shop manual you should have 3 wires going to your temp gauge.

A green blue (trace) wire from the sensor through the firewall to the gauge.  This wire does mix in with the main loom between the front of the engine and under the dash. Where ever it goes you can test for continuity before firing everything up.

A light green wire from the "I" (for instrument) terminal of the voltage stabiliser (which lives in the back of the speedo - so  doesn't need to pass through any holes in the binnacle) to the gauge.

And, a red white wire from the panel light switch (or any of the dash illumination lamps) to the terminal on the instrument lamp (which earths through the lamp holder/dash panel). 

Cheers, Ian

Here is how I am trying to wire my temperature gauge for a 1966 Austin Cooper S.

green/blue wire from wiring harness through hole in Speedo binnacle to gauge.
green wire from “I” post on voltage stabilizer through hole in Speedo binnacle to gauge.

The green/blue wire is too short to connect to the gauge terminal.

I just sourced a 8” green/blue wire (British Wiring) with female and male spade connectors.
When connected to the harness wire I am able to connect to the gauge terminal.

Not sure if this common or not.
If I wired incorrectly please advise.