I had something similar one time with a Novak speedo. It wouldn't work, but it worked in another car. i finally figured out, that it was a combination of a digital servo, and Novak receiver, and Novak speedo. Every item worked fine alone, but those three together just wouldn't work. I sent all of the item to the manufacturer, and they all sent them back and said they worked fine. The items just didn't work together. Something about the three items together caused massive glitching.