iv made not of the circumstances which these issues occur,
1. the fan cuts in at 90deg (or there abouts) and cuts out when its dropped below, so i would suggest the stat is opporating the fans rather than a faulty coolent temperature sensor.
2. when the fan cuts in there is a loss of engine power, no stalling, but emmissions sky rocket and electrics dim. The car has a good battery which the car fully charges, so i dont believe it is battery or charge related. I am going to look into the earthing as it could be an issue with the efficiency an earth. (if anybody has an engine bay earthing diagram that would be cool)
3. i recieve a bank 1 lambda error occasionally, this typically happens before the car is up to temperature, so cannot be caused by issue 2 as the emmissions are perfect when the fan isnt running. This happened both before and after a new replacement lambda. Its possible the new lambda has a fault, but seems like a strange coincidence that the new and old exhibit the same fault, i wonder if its possible for a fault elsewhere can cause both to display the same problem?
I have no experience with electronic testing equipment so im looking to teach myself, as it will be clearly invaluable with this car! any suggested reading would be greatly appreciated.