so i take it that the HVAC from the d2 will just be adding more problems. I guess that counts that out, and as u said, cold air is cold air :O)

The instruments on the other hand is something i'd really like!! i dont mind going a distance if i can get them to work, and work accurately.
any way around to get them to work with the mechanical 300tdi? any sort of special converters etc?

 

Most gauges from a D2 are driven by the ECU,

Tachometer is driven by ECU pin C0658-19 (TDI) or C0637-17 (petrol), is on OBDII port

Speedometer is driven by C0504-3 of the SLABS unit. Odometer has some linkage to other modules as it flashes if you have swapped out dash cluster. Speed is most likely reported to ECU and may be present on the OBDII port.

Temp gauge (a useless idiot light with a pointer) is driven by ECU C0636-44 (petrol) or C0658-7 (TDI). Available on the OBDII port, like with an Ultra Gauge. More accuate with a scanner or Ultra Gauge, as you get raw data, not filtered and processed.

Fuel gauge is analog.

D1 (GEMS) and D2 (Bosch) ECU are different, different harness, sensors, etc.

You will note in pix below that the D1 is providing tach and temp to the OBDII port, it also has speed, just not shown on this view of scanner. The Ultra Gauge is better looking, and lets you configure the display you want. It can also monitor the volts to the OBDII port, which gives you a charging system view as well. The Ultra Gauge lets you program alarm points as well, so your attention is drawn to high coolant temp instead of the bumper sticker on the Rover ahead of you. A little hard to see sometimes....