Did you ever get a resolution to your Tach problem? I have a brand new 6530 with less than 7 hours on it so far and I've caught myself having to tap the tach to get it to work. I can only think that's off to a bad start.. Also had a mystery starting problem. Acted like the neutral safety switches were acting up. I tried all teh usual things like shifting it in and out of gear, up and down the Hi-Lo, in and out of gear on the PTO. Also hand operated the PTO safety switch, then it just as suddenly decided it wanted to start again. Never had that problem on any of my other tractors, although my only experience has been about 30 years of dealing with old big tractors, other than a short term deal with a JD 4400 Which drove me to swear never to buy anything green again, which is how I ended up with the Mahindra.