Hey, I've had a small tacho for about a year that I hooked up myself and it works fine. I bought a bigger one (3.5"), same brand, SAAS, and it wires up the same way but I couldn't get a review signal. It lights up, remembers the colour it was on but the needle won't move. Thought it was faulty so I took it back and exchanged it for another of the same model but it's just the same. I've hooked my smaller tacho back up and that's working fine. Any ideas on what it can be? I've read the threads but can't find anything relating to this exact problem of the smaller one working but the bigger one won't.