The (new) radiator fan of my 1998 S40 2.0 works only when the AC is switched on. It doesn't activate even when engine temp reaches 98c. The AC works only in the 'auto' setting (a new resistor has been installed but the mechanic said the car needs a new AC control panel to solve this.) As a result the AC needs to be in auto mode in order for both the AC and radiator fan to spin in tandem.

Why is this happening? And as I wait for the new control panel to arrive, can I still drive my car daily despite this problem?

 

My radiator fan comes on at 214F which is about 101.5C.One fan turns on with the AC the other shouldn't.As far as I know there is no connection between the two.If you reach only 98C then yes you can drive.When you see the needle starting to move up from the middle then you should start to worry but apparently you don't reach high enough temps for the fan to turn on.Do you live in a colder climate?