TinyTach TT2A dead? Fit your own external 3v battery

My Tiny-Tach TT2A digital tachometer suddenly stopped working after only 2 years, without any warning - I cut open the faulty tacho and fitted my own 3v battery. It works great now. This 'dud' tacho was only 2 years in use, nothing like the 5-10 years that most reviewers have experienced with their Tiny-Tach units. _____________________________________________________________ On 4 February 2021, I found my Tiny-Tach had no LCD display and no response to the ‘Select’ button. This was very awkward, since I was due to leave that weekend on a 5-hour flight, in my CFM Shadow microlight aircraft, to a national fly-in. With no digital read-out, I could only guess what RPM the Rotax 582 engine was doing. Next day, I travelled to borrow an analogue Rotax tacho from a friend who lived 150km away. Tiny-Tach claims on their website that the 3 volt lithium battery in their TT2A model has a 5+ year battery life, probably longer. They say that the battery is not replaceable, because the tachs are potted and cannot be opened. Although very low draw, the battery is always on, and will display the hours when the engine is not running. If there is no display, the battery is dead. ______________________________________________________________ After-sales Service from the Factory: I repeatedly emailed various people at the Tiny-Tach factory "Why would the battery be dead after only 2 years?", but they didn't answer that question. One employee just suggested that I try the factory reset procedure. I did this reset, but no luck. Again I pleaded with them "Please can you help me get a functioning tacho again?", but never any reply (even after follow-up emails). Very unhappy with the factory's response, so I decided to open up the back of the tacho and investigate replacing the battery myself or wiring in an external 3v battery. Good news. It's very easy to get inside and wire in a battery (or replace the 'coin' battery if desired). Enjoy the video. ________________________________________________________________ Manufacturer: DESIGN TECHNOLOGY INC. 768 Burr Oak Drive, Westmont, Illinois 60559, USA Website: https://tinytach.com ________________________________________________________________ NOTES: I purchased the TinyTach TT2A from the USA factory in 5 December 2018 and fitted it to my ultralight aircraft on 6 February 2019. I enjoyed using the TT2A when flying - it had a very easy-to-read display and I think it is more accurate than the previous analogue tach. Installation: TinyTach was installed correctly as per instructions (Red wire 1 turn around plug lead. White wire bolted to engine block.) Never connected to any voltage Display unit is undamaged Coax cable still in excellent condition Unit always kept dry (inside an enclosed cockpit) Aircraft stored inside hangar Mild climate (temp averages 60 deg F)