Heater fan controls, 4 wires to fan

[tombayley143]

In a 03 plate 2 litre multispace diesel

Hello, the speed controller for the fan was temperamental, so I removed the control unit and cleaned all the contacts and replaced, now doesn’t come on at all, connecting the green and yellow wires makes the fan come on full but can some one supply a wiring diagram or explained how it the speed controller works components inside are not high current so can’t drive fan directly!

Or can I just add a switch to have on or off as this is better than none!


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[cancunia]

The wires may go via a resistor pack to give the different speeds, IIRC full speed will go direct to the fan. Some cars have a diode pack which is prone to failure. If you search on here for heater problems, you'll probably find both systems posted. Ebay has pictures of both.