[crossy]

whew you new guys are really testing my typing skills, Actually I have no typing skills so I saved all this stuff a while back. And just so you know. this is exactly what i send to someone that is elling a tach and over half of them never reply back, prolly because they know the one they are sending is bad.
TACH TESTING ,

Hello, I am interested in the condition of the tach. They are very expensive to repair. They are also commonly bad. If you look closely at the back of the tach you can see the markings as to where each lead needs to go. COIL,GND, 12V. They are very easy to hook up and test on an V-8 engine especially if you have one around with an HEI distributor . ( HEI's have a 'TACH' terminal right on the distributor cap.). if you have anything around with the old points distributor then the terminal marked COIL of the tach goes to the (-) side of the coil. the 12V terminal of the tach and GND terminal are kinda self explanatory. You need any 12V power and a ground .. if you do not have original wiring pigtail then a .250 female spade crimp-on connector on the end of a wire works fine. I would be very likely to bid if I knew that it worked . Since I redo these dashes and hobby at 73-87's I know a bit about them. 60% of the ones I have bought are bad so I know all to well what I am asking for here. when they START to go bad they read high, like 1200 RPM at idle, and get worse as RPM goes higher. Having a known good tach in the vehicle to compare it with is a real plus. I have bought more than one that the person tolds me 'works' only to find out that it is way off on readings. At idle you should see 500-800 RPM and a quick tap of the throttle should see 2500 RPM or so. As some go bad the needle responds very slow to RPM increases or 'stick' as they move forward. when they really get bad they will bury immediately or not register at all., I am more than willing to pay/bid fair money for known working units. lemmeknow, thanx , DAVE