I have been playing around with different sensor gaps today,originally the gap was 1mm and the Speedo worked fine until stopped in traffic or the weather was hot when the Speedo fluttered or died until it cooled.Dropped the gap to 0.8mm the led was on all the time,opened up to 0,8-0.85 but Speedo flickered at 30 mph increased gap to 0.9-0.95 and the Speedo works fine.Not been stuck in traffic and not too hot today so I am not holding my breathe that it's fixed.The variation in the gap at any one setting is down to the gear wheel run out.Not sure what happens if the gap is larger than 1mm, I think it was over that when the problem 1st arose ,in my ignorance I never checked the gap before reducing it.Not sure if increasing the gap will help.