Since it runs off the W terminal on the alternator, I wonder if there are issues with accuracy. When I calculate by gear ratios and tire size, and measure my speed with a GPS (speedo is accurate to within 1mph), the calculated rpm for 60mph is about 2550, but the indicated rpm is 2900. What's the best way to check tach accuracy?
Thanks for the help. It sounds like there may be an adjustment through a potentiometer existing (or does one need to be added?). I guess I'll take a look when I pull the cluster to repair the intermittant odometer.