Re: How to install water pressure gauge and/or tempurature gauge.
"B" is an overheat sensor. It is usually a modified 14 x 20 screw, but yours looks different than stock.
The overheat sensor (on the engine) is a switch that is always open until high temperature causes a bi-metal switch to close to ground. So knowing that, you can infer with very little electrical knowledge that:
1. One wire of your overheat indicator (near, at, or on the dash) should connect to the "I" terminal of the ignition switch for power only when the engine is running
2. The other wire of the overheat indicator connects to the ORANGE wire in the cable from the engine.
3. The orange wire inside the engine connects to the terminal on the overheat sensor.
Operation is thus: With the ignition key in the run position, power is always delivered to the indicator and through the orange wire to the sensor, but until the sensor closes, the power has nowhere to go and the indicator is silent or not lit (depending upon whether you have a buzzer or light)
Once the sensor closes due to overheat, the power can now go to ground and the indicator buzzes or lights until you turn off the ignition switch.
To test the indicator, you short the terminal on the sensor to a good ground like a spark plug body or a bare bolt with a short piece of wire or a screwdriver etc.
To test the sensor, with the ignition key on, you must either overheat the engine or heat the bottom of the sensor with a butane lighter or a propane torch being careful not to melt it. When it gets hot enough, the indicator should sound.
You can use the orange wire for overheat indicator OR temperature sensor and gauge but not both at the same time. If you want to have both, you must either run another wire or use the purple if you do not have a tach. (obviously, you must disconnect it from the rectifier). If you are not using the black ground wire it can be disconnected from the engine terminal and used for temp gauge. HOWEVER, to avoid confusion, it is preferable to run a separate wire.
