HI my 2007 2.0 tdi 170 has developed a strange fault.When driving it has an intermittent surge of power of about 100 rpm.It does not do it all the time but when it does the temp gauge drops to the bottom of the scale.Sometimes the gauge takes a while to work but other times it works ok with no surge.I thought the sender was faulty and bought and fitted a new one from Euro Parts but it made no difference.I have also noticed that sometimes the electric fans are running when the gauge is at the bottom but stop when the engine is switched off.I have a new radiator fan switch but have not fitted it yet.I have done a scan but there are no fault codes relating to the cooling system.I drove the car with the diagnostic too in live data mode and every time the fault happened the engine temp reading on the tool dropped to the -20s or lower and then returned to normal.It feels like a broken wire in the temp circuit connecting and disconnecting but I wouldnt know where to look.Can anyone give me any info on this problem.