A tachometer is an instrument which is used to determine the rotational crankshaft speed of an internal combustion engine. A figure representing Rotation per Minute (RPM) of the crankshaft is arrived at by measuring and processing the voltage drop across the ballast resistors of the ignition coil of an ignition system of the vehicles.
When fuel and air burns in an internal combustion engine, it creates enough pressure to drive the piston to-and-fro inside its cylinder. This makes the crankshaft connected to the piston rotate.
The tachometer indicates the RPM at which the crankshaft is moving, which very is useful in deciding when to change gears while accelerating as well as braking. This helps the driver of the car in making efficient use of the engine by avoiding overheating of the moving parts of the engine, which could lead to car engine problems and damage.
How to Install a Tachometer
You may be referring to the instructions for the purpose of installing a tachometer in your car for the first time. On the other hand, perhaps you are interested in replacing your car's current faulty one which has gone through all possible troubleshooting, and is declared beyond any repair. Now, you can save money by doing it yourself.
There are different types of tachometers available in the market. It depends on the number of cylinders (4, 6, or 8) your car's engine employs to generate the necessary horsepower. Alternatively, you can also purchase one which can be used with any number of cylinders by employing switches on it.
Go through the instruction guide that comes along with the instrument, and be sure to know where the wires (green, black, red and white) leading from the tachometer are to be connected. Decide a place on the dashboard where it will be easily visible after installation.
- Park the car in a place where you have sufficient light. Keep a portable or work light source handy, you may need it for identifying the correct wires to make proper connections.
- Identify all wiring junctions in the engine compartment and under the dashboard that will come into play during the task.
- Mount it using mounting brackets in the place selected for it and run the wires from it to the firewall behind the gas pedal.
- Identify the wires (most probably green or black) leading from the tachometer to the engine bay and let them through the firewall. Use insulation tape if necessary to protect and secure them against the sharp edge of the hole.
- Ground the black wire by connecting it with the battery ground of the car. It will ensure its proper working.
- With the help of a tachometer adapter or connector, hook the green wire into the negative terminal or post of the electronic coil or ignition system.
- Hook the white wire to the switch (12 volt) that controls the inside lighting of the car or the dashboard lighting.
- The red wire needs to be hooked into the ignition switch (12 volt), so that it starts working when the car is switched on.
- Whenever you are splicing the wires into the existing ones, try to make the connection permanent and avoid short circuits or poor performance. If the need arises, use T-splice wire adapters to do so.
After the crankshaft has achieved a certain RPM, the gear need to be changed for better fuel economy, and the tachometer's reading helps the driver in deciding when to do so. The instructions are easy to follow and helps one to save money on car repairs and also fuel consumed everyday.