Re: How to test a tach?
Ive searched around and cant find a way to test a tach with it out of the boat. When i turn the key on all the gauges move except the speedo and tach which is stuck at about 100rpm. I know my speedo is bad because I can blow into the tube on the back and it doesnt move.
Incorrect. The speedo doesn't move because you can't generate enough pressure to move it.. Use compressed air at low pressure and I'm sur eit will move.
CatriderF7 said:
Im guessing the tach gauge has also failed but would like to confirm this thru testing before ordering a new one. Can I test voltage at one of the wires when I turn the key on to make sure it has power? I cant start the boat now because of where it is under my carport with all my tools and in need of a new axle on the trailer before I can move it. The tach has 3 wires running to it. Im guessing theyre power, ground and signal from the engine but not sure. The boats a 1999 Bayliner Capri 2050
Quite correct. Check you have power and ground on the tacho, then check continuity of the gray wire from the coil '-' to the back of the tacho. If you want to test it outside the boat, find a car with points ignition and hook it up. Or build an astable multi-vibrator circuit that you can vary the frequency (I'd use a 555 timer chip) and have it drive a relay to fire a coil... Hook the tacho to the coil with an oscilloscope and run it up... You can measure the frequency on the CRO to know what the tacho should be reading....
Chris..........
(Don't forget to allow for the fact that a 4 stroke (I assume you have a 4 stroke as you only told us what boat you have, not what engine is in it) that only fires half the cylinders per revolution)...
