Erm, I made my own "harness". I wonder what's in that Tdi harness to change things ?
From the wiring diagram, the TD5 wiring to the temp gauge is different to the Tdi in that the sender wire is routed via the speedo, in on pin 5, I think and out on pin 9 on the c1061 connector (the lower one) on the back of the speedo. The wire from pin 9 then goes to the ground terminal on the back of the temp gauge. On the Tdi according to the diagram, it goes from sender straight to the ground terminal bypassing the speedo.
Stu and I tried both today, getting low reading on the tdi set up and nothing on the td5 set up, so next stop is a late 300 sender.
Thanks guys
Mo