The importance of the fan resistor & maintenance.

As you can see in the picture aside, the switching resistor should be green. This insulation is very important component, namely the isolation of the resistor , it must therefore be in good condition. For that reason you should regularly check the condition of the resistor. In this way it is possible to check when the insulation is worn out.

Why is this so important?

When the insulation material is worn out, the pressure on the fan is too high and it cannot reach the intermediate position in terms of rotational speed. This creates too high a pressure on the air conditioning system, namely from 15 bar to (often) 25 bar. This increased pressure causes overload on the air conditioning compressor. All this together has the consequence that the entire air conditioning pump can break down (which is a very expensive part compered to the fan reistor).

The resistance causes a different resistance (in omega) for each position of the fan. From this you can recognize that the fan positions are not working properly. Still, it is better to check the resistances in advance. If this happens too late, the air conditioning will be damaged, as mentioned before. The operation of the air conditioner is deteriorating. The air conditioning can then dissipate less heat as a result of the malfunctioning fan. The temperature of the engine will fluctuate as the air conditioning weakens. The intermediate position of the fan has disappeared, so that the motor can become either too hot or too coldFrom this

The figure aside shows three switching resistors in three different conditions. At the left resistor you see that the insulation has little to no wear and at the right resistor the insulation is completely worn out.