First be aware that temperature sensors have an extremely low failure rate because there is just one component inside them. The circuits have more trouble with corroded connector terminals and cut or bare wires, but that would be detected and a diagnostic fault code would be set.
I assume your 90 - 100 degrees is Celsius. That would be the normal range. If your gauge is going too high, that is being reported by a properly-working sensor doing what it is supposed to do. Replacing the sensor will not fix the overheating problem. If you hear your electric radiator fan turn on, that proves the entire circuit, including the sensor, is working.
Also, most engines of this time period used two coolant temperature sensors. The single-wire sensor is for the dash gauge and has nothing to do with the radiator fan. The fact your gauge is working proves that sensor is okay. The engine computer uses a two-wire sensor. It is that one the computer looks at to know when to turn the fan on. It also has a very low failure rate.
In later years most vehicles stopped using the single-wire sensor for the dash gauge. Instead, the instrument cluster gets its information from the engine computer. Regardless if there is one or two sensors, they are usually on or right next to the thermostat housing on most engines. There are some variations, but the thermostat housing is most commonly at the engine end of the upper radiator hose.
To test the fan system on most cars, just unplug the two-wire coolant temperature sensor while the ignition switch is on. That will set a diagnostic fault code, but since the computer recognizes a problem with the circuit, it will turn the fan on by default in case the engine is too hot.
To add to the confusion, your car should have two fans. Just because you hear one turn on when the air conditioning is turned on, do not assume that is for the radiator. When there are two fans, usually one is for the radiator and the other is for the AC condenser.
Friday, June 16th, 2017 AT 2:08 AM