Each motor rotates within the limits of its design. The pistons inside the engine pump the crankshaft to make it turn. This movement sends horsepower to the street. A tachometer counts the number of revolutions per minute (RPM) of the crankshaft. It can also be used to change gears at the right time during acceleration and braking. If the RPM of an engine is allowed to leave the specific limitations, the moving parts will begin to generate enough heat and friction to damage them. Use a tachometer to know when to change gears and when to stop accelerating an engine.
- Look for an open and level surface to park the vehicle where there is plenty of light. Keep your tools and safety equipment at hand during the installation of an electronic tachometer. A flashlight is recommended when working in dark areas under the dash and the engine compartment. Locate all wiring connections and prepare the tachometer for installation, arranging the cables to be easier to pass to connect their connections inside the passenger compartment and the engine bay.
- Install the tachometer wiring around or through the instrument panel to the firewall behind the accelerator pedal. Use clamping bands to secure the tachometer cables in the car’s chassis. Separate the cables that will be connected inside the passenger cabin and those that will be connected in the engine compartment through the firewall. Install the tachometer on its mounting bracket where it will be secured on the board. With the tachometer and wiring in place, finishing the job is easy.
- Use an existing hole in the firewall to pass the black and green wires through the motor bay. The existing holes will have a rubber washer to protect the wiring. Cut a notch in this washer to pass the cables or drill a new hole for these. Once finished, this hole can be created waterproof with a silicone gasket gel that keeps it dry around the hole and wires.
- Connect the black cable of the tachometer to the ground of the vehicle’s battery. Continue using tie-down straps to secure the tachometer cables on the outside of the engine compartment and up to the battery junction box. A secure ground connection will help the tachometer work properly. Connect the green wire to the negative terminal of an existing electronic coil or electronic ignition system with a tachometer adapter as a connector.
Connect the white wire to the interior light switch, which will illuminate the tachometer when the headlights are on. The red wire is for the ignition switch. Connect this cable so that when the car is turned on the tachometer starts working. T-splice cable adapters allow you to splice new cables with existing ones using pressure connectors that you will fit around the existing cable to make the connection.
Installing an outboard tachometer
An outboard motor is an independent unit, mounted on the outside of the boat, containing the gearbox, the engine and the propeller. The tachometers measure the number of revolutions per minute (RPM) of the engine. The installation of the tachometer consists of the placement and correct connection of the cables.
Using a small screwdriver, gently press down and turn the selector knob on the back of the tachometer to the exact position that matches the number of alternator poles. Fix the selector button by gently turning it back and forth with the screwdriver.
Before installing the tachometer, disconnect the battery. Position the tachometer no closer than 18 inches (46 cm) from a compass and drill a hole in the dashboard. Mount the tachometer with a clamp.
Use stranded, marine-approved stranded cables, 18 AWG (American Wire Gauge or American Wire Gauge) or more burdensome. Connect a cable to the tachometer battery and secure it with a washer and nut. Connect the opposite end of the cable to a 12-volt direct current (DC) circuit that is activated with the ignition switch. Connect a cable to the tachometer signal post, secure it with a lock washer and nut. Connect the opposite end to a wire or terminal that originates on the alternating current (AC) side of the alternator. Connect a wire to the ground bolt of the tachometer and secure it with a washer and nut. Connect the opposite end to the electrical outlet of the boat located near or on the instrument panel. Connect the antlers terminal, which is located near the lights assembly.
How to install a tachometer on a motorcycle
Wiring your new Autometer tachometer in your vehicle will complete the installation. Once you have selected a mounting location, you can run the four cables that operate the tachometer. The tachometer is designed to show engine RPM or rotations per minute. Autometer has designed its tachometer to be used with four, six and eight-cylinder engines with the only requirement that you must calibrate the tachometer during the installation process.
- Calibrate your Autometer tachometer to the size of your motor as indicated below. If you have a four-cylinder engine, cut the two cables in a loop on the back of the tachometer with pliers. For a six-cylinder engine, cut only the brown wire and for an eight-cylinder engine do not cut any of the wires.
- Extend the red wire on the back of the tachometer to the fuse box of your vehicle. Select an open-source power source in the fuse box to connect the red wire. Most fuse boxes have several positions in the fuse box that will allow you to connect a cable to these with a shovel. Check your owner’s manual for a key that indicates what is available in the fuse box.
- Strip about 3/8 inch (0.93 cm) of insulation from the end of the red wire with the wire stripper and insert the wire into the crimp connector. Engage the connector on the cable with a pair of crimping pliers and insert the connector into the selected slot in the fuse box.
- Extend the white wire of the tachometer to the wiring of the instrument lights. Connect the white wire to this cable using a wrench for a crimped cable. Close the two halves of the connector around the white wire and the clear wire of the instrument. Press the metal key into the connector with a pair of clips and place the cover over the closed connector.
- Pass the green and black wires out of the cabin through the firewall. Run the black wire to the negative terminal of the battery. Peel the end of the black wire approximately 3/8 inch (0.93 cm) and install a crimp connector. Connect the ring connector under the retaining bolt to the battery terminal and tighten the bolt with a wrench.
- Execute the green wire on the negative side of the coil. Strip 3/8 inch (0.93cm) of cable insulation and install a ring connector crimped into the cable. Remove the nut on the negative terminal of the battery with a key and install the green wire on it. Replace the nut and tighten it with a wrench.
Tachometer wiring instructions
The tachometers calculate the number of turns the crankshaft of your engine makes every minute, expressed in revolutions per minute (rpm). The installation of your tachometer requires some electrical connections. You must connect four cables, one to the battery terminal, one for the vehicle wiring harness, one for the instrument panel lighting circuit and one for the ignition coil, to complete the installation of the tachometer.
- Connect the black wire to the negative terminal of the battery or clean unpainted chassis ground. If you use the latter, the tachometer may work inconsistently, since the black wire connection is under the dashboard and due to ground connections, in addition to the negative terminal of the battery, are prone to malfunctions.
- Connect the red wire to a wire in the vehicle harness that has full battery voltage when the ignition key is turned to the “On” position (however, do not make the connection while the ignition is in that position).
- Insert the white wire into the circuit of the lighting device of the panel or of the line that controls the panel of the intensity regulating device. Keep in mind that imported vehicles are already equipped with attenuator control in the lower part of the panel lighting device circuit.
- Connect the green wire to the negative part of the ignition coil, if you have an engine with distributor-equipped, which should have come with a one-winding package. If you have a distributor-free ignition system, consisting of multiple packages of square or rectangular ignition coils, sensors and computer controls, connecting the green wire to the ignition will depend on your engine and ignition system. In this case, contact the manufacturer of your ignition system or ignition coil for more information on how to connect the green wire to your tachometer.
Check that you have secured all the cables before starting the engine of your vehicle.
Protects the wires that will go through the firewall from damage caused by the sharp metal edge of the firewall hole. Wrap the contact point with extra insulation tape and use the silicone gel to support the wires in the center of the access hole.
Connect each new cable to the existing ones so that there is a permanent connection. Avoid short circuits and poor operation of the tachometer making the right connection from the start.