On all vehicles except 1990-91 ACCORD, the fan switch is located at the base of the radiator. On 1990-91 ACCORD the switch is located at the rear end of the cooler connecting pipe running outside of the engine just above the oil filter. Apart from the switch, there are no other electrical components in this place, so it is not difficult to find it.
1. With the ignition off and the engine cold, drain the coolant from the radiator to a level below the location of the sensor. For all cars except 1990-91 ACCORD this means that the radiator must be empty, so you will need a large enough container to collect the coolant.
2. Disconnect the sender wiring.
3. Extremely careful not to damage the heatsink or sensor mount, remove the sensor by gently unscrewing it.
4. Install a new sensor and screw it in with a force of 23 Nm. For 1990-91 ACCORD the gauge is screwed up to 28 Nm.
5. Connect the wiring to the sensor.
6. Fill the radiator with coolant.