Still having trouble with my cooling control unit, I think maybe the guys that did the chassis work may have been arc welding on the chassis without disconnecting it first.
As a testament to Tatra Trucks I sent an email yesterday looking for the circuit diagram of this unit and at 7:15 this morning i had a reply with the circuit attached. That's customer support.
At this point i have all the sensor circuitry working again, just need to get the fan control working now.
Here it is on the bench, note the resistors simulating the temp sensors and the test switch to simulate a fault.