Here's the situation - with a GRT EIS - take off is normal until the "out of range" warning light illuminates. A quick look at the EIS identifies the issue: 9000 rpm. That's not possible with the nose up and a constant speed prop so the heart rate goes down to normal. A little investigation reveals that the rpm indication goes crazy at a true rpm of just over 4100. The tach indications are fast changing, unpredicable and wide ranging - always between about 5000 and 9000. Bring the throttle back under 4100 and everything is normal. Above 4100 and it goes crazy again. Same symptoms on three after-inspection test flights. 58 hours TT. All connections on and between the tach sensor and the instrument are soldered. A visual of the solder connections does not reveal any appearances of a cold solder joint.

As always, your ideas, experiences and suggestions are appreciated.

Thanks, Darrel