The heater blower/fan only works on position/speed 4/the max. Do you have any ideas why? RENAULT TWINGO I (C06_) 1.2 16V (55 kw / 75 hp) (01.2001 - 06.2007)

The issue you describe with your Renault Twingo heater fan working only on the highest speed (position 4) and not on the lower settings is very commonly caused by a faulty fan resistor. The fan resistor is responsible for controlling the lower speeds of the blower motor by providing different levels of electrical resistance. When this component fails or overheats, usually the lower speed settings stop working but the highest speed will still function because it bypasses the resistor.

From available information and user experiences:

- The fan resistor can overheat and burn out, especially if the blower motor itself has issues (like seized bearings causing extra strain on the resistor). This leads to the resistor's thermal fuse blowing and cutting power to lower speeds.
- The resistor is usually located under the dashboard near the blower fan, and its removal involves unscrewing a couple of screws and pulling it out.
- Replacing the resistor often restores the lower fan speeds.
- It's also recommended to check the fan motor condition because a failing motor can cause repeated resistor failures.
- Additionally, checking fuses and relay related to the fan circuit should be done as part of diagnosis, but the resistor is the most typical culprit in your symptom.

So yes, the problem is very likely to be with the fan resistor if only the max fan speed works. Replacing it should solve the issue. If you replace the resistor and the problem persists, then the blower motor itself or wiring could be to blame.