Hi All What a stupid thing to fail on, but not having a working speedo above 30 mph is fair justification, and its not as if they didn't give me enough time and attempt to get it working. In fact the IVA guy bent over backwards to help, but eventually time bet me. So I know that the sensor has to be 1 - 1.2mm away from the sensor ring, but I didn't have any reliable way the measure this during the time given to fix it during the test. Before this turns into a Caterham bashing thread, they didn't road test my car, under my instructions because of the salt on the roads, and it wasn't driven to the test. The next time it wil be driven is for the retest, and it would be nice to have some confidence that my £90 retest fee is going to be worth it. So the symptoms Test 1 : Sensor very close, no visible air gap but no contact with the ring (as adjusted during PBC). The speedo would get to 10-15 mph and refuse in increase. Test 2 : Sensor gap adjusted by me, but to far to ready any speed. Test 3 : Sensor gas adjusted between the two, this time I could get the speed to 20mph driving around the test centre, and up to 30mph on the rollers before the examiner jumped in to perform the test. All was fine up to 35 mph, the speedo then died to 0 mph. I did observe during my limited time driving around the test centre, when the clutch was pressed the speedo died to 0 mph, very strange given the clutch its not connected electrically in any way, I also want to point out I an not ruling out wiring faults because my car was wired incorrectly from the factory on initial startup. However the manuals wiring diagram it a little out of date I feel. I know I am going to adjust the sensor again, this time with more tools and potential for accuracy. I am going to check the signal at the speedo and the other point I have found in the loom, hopefully with an oscilloscope, if I can find one. I just can't explain the clutch / speedo connection, and nor could the Caterham mechanics I spoke to post IVA. And yes they would rectify it if I left it with them, but I am not doing that until the weather is better. So this is just about working out what the problem is/might be before a retest. Hope someone can add any perls of wisdom or other areas to test. Chris.