C320 V6 2001 Fan constantly on!

[ngenius1]

A friends engine fan is constantly running as soon as you start the car till you take the key out.
The cooling fan motor and resistor have been changed, but still no joy.
Any ideas?
Thanks in advance.

 

[BlackC55]

Is it running at full yield?

 

[ngenius1]

yes at full speed

 

[BlackC55]

There is a problem with the engine electrics and the fan runs at full speed incase of engine overheating as a precaution.

Most of the time its because a sensor is out of spec or the engine control unit is kaput.

 

[ngenius1]

The sensor and the control unit has been changed, it was put on a mercedes computer and they said that was the fault, the fan is still running.
Any other ideas?

 

[david55amg]

Is it on because your air con is on. Try turning that off first.

 

[markmifsud]

When I disconnected my MAF to see the effect without it, it powered up the fan constant also. So as blackc55, sensor failure. get it on a star to see what one