When the cooling fan is not working and the fuze and the relay is good...and how to fix it...?

Check the wiring harness to the fan they sometimes put a fuseable link in the wire and it might of blown.

Sounds as if,the cavalier,may have an internal blown head gasket.

The selector switch on the dash controls the blower motor relay, then the fan switch controls the speed. The fan switch gets power from a 40amp fuse and the control panel gets power from two other fuses.
If you are working the control switch to get the fan to work, the control switch may be failing.

disconnect the plug at the fan,, supply the wires that go to the fan with 12 volts direct,, if the fan starts,, the fan is good, if not replace it,, now if its good,, follow the system back,, go to the fan replay, check it, ( sometimes you will have 2 or 3 of the same relays in the under hood fuse box, just switch them out so that the fan has a good one, ( known to work) if this fixes the problem, replace the relay

the cooling fans on your car are comanded on by the engine control module which reads engine temperature from the temperature sensor . when comanded on the engine control module sends a signal to the cooling fan relays . which in turn runs the current to the cooling fans . So you might want to check the cooling fan relays and make sure the fues for the cooling fans are good and the relays .if the cooling fan fuses and relays are good it could be a problem with the fan motors or the engine control module not reading the right temperature in that case it could mean you have a problem with the temperature sensor

The low speed side of that relay is the most common failure point in this system. Usually you can still hear the relay click, but the contact points are burned away.
I am not familiar with the Z3 fuse box, but the the first step in the diagnosis of that circuit is to pull the wire off the temperature sensor in the radiator. Use a paper clip to jumper from the high and low speed wires to the ground wire (ground is usually brown on BMWs). You will probably hear the relay click and the fan may or may not come on for either speed. If it clicks but the fan does not come on, and you know the fan works, just follow the sound of that click and replace the relay.
If the relay does not click, it may still be a relay problem, but check your fuses before replacing the relay..

Your cooling fans are not running when they should be (one is sensor controlled and runs at need) the other one manually comes on when the A/C is turned on so that fits with hot when idling and cooler when moving (you get some air flow while moving). The fans have relays and fuzes that should be located and checked. Once the relays are verified or replaced then the fans should run. If they still do not run perhaps they need replacing. DJP

The horn maybe a horn relay,or a bad horn,or the horn button .The cooling fans,check to see if they will come on with the ac on,if not,check the fuses,and the cooling fan relays,if the cooling fans come on with the ac,then change the coolant sensor.

A lot of different things fall into this senario.Low coolant level,air in the cooling system,and a stuck thermostat,or,a bad coolant sensor,or even a bad cooling fan relay,or the cooling fans are bad.Turn the defrost on or the ac,the cooling fans should come on if the fans,and the relay are ok,if so,replace the thermostat,and coolant sensor,and bleed the cooling system of air.

In the fan circuit...You have a temp switch screwed on the radiator, a fuze and a relay in the fuze box plus a fan.  Swap the relay with another relay, replace the fuze.  The other fan should come on when the a/c is turned on.  If you fix the fans and it still overheats, you may have a BLOWN HEAD GASKET.  ALSO ARE YOU BLEEDING THE AIR FROM THE SYSTEM?  DO YOU SMELL EXHAUST IN THE COOLANT?