I recently purchased a Teleflex universal tach for my Merc 850. The original tach has not worked since I owned the boat. I installed the new tach as the instructions described. It worked fine.<br /><br />I thought I would try disconnecting the battery to make sure the motor ran fine on its own without battery power. When I disconnected the battery, the tachometer started smoking. It stopped working altogether.<br /><br />I got out my multimeter. There's 3 wires going to my tach: ground, 12V (ignition), and 'send'. The 'send' is normally supposed to have about 7 volts. However, the 'send' jumps up to 12 volts when I disconnect the battery... it returns to 7 volts when I reconnect the battery. This is all while the motor is running of course. It is the 12 volts that went to the 'send' that fried the tach.<br /><br />Is this normal? Should my 'send' jump up to 12 volts when the battery is disconnected? It kind of makes sense, because the battery is no longer being charged by the motor.<br /><br />I don't want to fry another tach... I'm wondering if something is connected incorrectly or if something is wrong with my rectifier. Maybe it's normal.<br /><br />Thanks
