A tachometer is an instrument that indicates the RPM (Revolutions Per Minute) that turns the engine of our car, and although it is not a luxury many instrument manufacturers do not include in-dash models by lower costs of production.
The purpose of the tachometer is to know what is the limit of revolutions per minute at which the engine to shift gears or accelerate stop working.
Years of experience have taught us to drive cars without tachometer "HEARING" listening to the sound emitted by the engine, and if you hear "VERY ACCELERATED" shift gears or fail to accelerate.
But if we have already taken the decision to install a tachometer in our car we should know a few things before you even buy it in any case if you already have one no matter, we simply understand how to connect it to function properly.
The market offers a variety of tachometers and marks but all basically have the same working principle.
There tachometer needle or clock, digital tachometers presented numerically in revolutions either LCD display or LED, lights of different colors.
Tachometers also differ in how they collect the signal from the RPM of the engine, in a case of taking the sample electrically some point circuit high voltage generation while others do inductively high voltage cable of a spark plug.
A tachometer that picks up the signal inductively is very easy to install because the meter where you want it fixed, feeds the 12V electrical system of the automobile and the pick tip signal is set by way of the cable lock on a spark plug and that's it
Tachometers collecting the signal that required electrical connection connecting a GREEN CABLE (USUALLY) IN PRIMARY COIL high voltage supplying the spark plugs, this is what you should consider regardless of whether the generation circuit is a high voltage coil or multiple coils rotating as in the case of electronic distributor distributor.
This requires identifying the block high voltage coils and connect the GREEN WIRE one primary cables to take the RPM signal.
Not connected in A and C simultaneously as a short circuit for signals of high voltage generation occurs.
Nor connecting the center point, it corresponds to the 12V electrical system of the car and there is no presence of the ignition pulses.
Must also connect the power cables to 12V (black and red) tachometer.
Some models of tachometers bring other cables for lights on the dashboard that indicate ranges of RPMs, green: OK, yellow: and red CAUTION: DANGER, or even bring the lights around the tachometer.
Do not connect any cables to the side of the spark plugs, as the voltage is very high, around 25,000 volts, and damage the tachometer input signal.
All this is summarized in the following diagram, it is necessary to mention that the tachometer should after the ignition key auto feed, such as from the internal fuse box, can be 12V from the fuse radio.