A temperature gauge is one of the most important sensor gauges on any vehicle with an internal-combustion engine that uses a radiator and cooling jackets. Engine temperature directly affects combustion and moving internal parts. Without a temperature gauge, the engine would be subject to various modes of heat without the operator's knowledge, and this could lead to bearing failure and engine seizure. A vehicle owner can wire a temperature gauge in his or her vehicle in a drive or garage.
Place the vehicle in neutral and set the hand brake. Raise the bonnet and disconnect the negative battery cable with a socket. Refer to your owner's manual for the location of your existing temperature sensor wire. Some are connected to the top of the thermostat housing, attached to a sensor probe. Other wires can be found in the side of the engine block, where the sensor probe screws into a mounting flange. Remember the location.
Search for a location on your dashboard for the gauge. Make sure no components exist behind the mounting location. Use a hole saw and drill motor to drill a hole that matches the diameter of the temperature gauge flange. Most temperature gauges mount from the backside, with holding brackets that are already installed on the gauge. Fit the gauge in the hole to size it, then remove it. Detach the small gauge bracket with a socket if it doesn't fit initially.
Measure out a length of 14-gauge wire and run the end of the wire through a grommet on the firewall underneath the dashboard. Pull the wire through from the engine compartment. Route the wire until you reach the sensor position.
Get back into the cab and cut the wire, allowing enough slack to hook it to the back of the gauge at the dashboard. Run the wire through the back of the gauge into the driver's compartment. This will be the "Sender" wire.
Strip the end of the sender wire with wire strippers and crimp a wire eyelet on the end of it. Place the eyelet over the gauge stud marked "S." Connect it to the sensor probe. Tighten the nut with a socket. Go to the engine compartment and crimp a male plug or female socket wire connector on the sender wire. Connect it to the sensor probe.
Look for a screw under the dashboard that is attached to the metal frame. Remove the screw with a screwdriver. Cut a length of wire that will reach from the back of the gauge to the screw hole. Strip both ends of the wire, which will be the ground wire.
Crimp two wire eyelets to each end of the ground wire. Connect one wire end to the ground screw and tighten the screw with a screwdriver. Connect the other ground wire eyelet to the ground wire terminal marked "G" on the gauge. Tighten the nut with a socket. Locate your fuse box inside the passenger cabin.
Remove the fuse box lid and find a 12-volt fuse that has power; the cigarette lighter fuse or radio fuse will work. Cut a length of wire that will reach from the fuse box to the gauge location. Strip both ends of the wire. Twist one end of the wire and place it under the spade fuse connector.
Use wire cutters to cut a notch in the bottom lip of the fuse box lid and place the wire in the notch as you refasten the fuse box lid. Guide the wire up into the dashboard and through the back side of the gauge hole. Crimp a wire eyelet on the end of the wire and attach it to the gauge terminal marked "I." Fasten a nut on the gauge terminal with a socket.
Push the gauge into its mounting hole. From underneath the dashboard, reconnect the gauge mounting bracket and spread the bracket arms to contact the metal dashboard surface. Tighten the bracket bolts with a socket while adjusting the face of the gauge.
Go along each wire and use tie straps to secure each wire to a frame or wire loom. Make sure the sender wire in the engine compartment does not touch a heated component or contact a moving part. Reconnect the negative battery cable and start the engine. Note the function of the temperature gauge as the engine warms up.