The cooling fan in a Chevy Cavalier is thermostatically controlled--its operation is not dependent on air conditioner operation. When the air conditioner is operating, it's necessary to operate the fan continuously to dissipate heat from the air conditioning condenser. Without the fan, the air conditioner would fail to function properly. Whenever the vehicle comes to rest, there is no relative wind passing through the radiator, causing the temperature to rise. The fan will come on and maintain an optimum temperature.
Disconnect the electrical plug at the cooling fan. Connect the jumper wires to the electrical plug terminals on the part of the harness leading to the cooling fans. Hold one of the jumper wires on the negative terminal of the battery and briefly touch the other wire to the positive terminal. The fan should run if it is good. The polarity is not important. If the polarity is reversed, the only thing that will happen is that the fan will run in reverse. The only concern is whether the fan is good. If the fan fails to operate, it needs to be replaced, as this is the problem. If it operates, re-connect the connector and continue the diagnosis.
Locate the coolant temperature sensor by following the upper radiator hose down to its connection point on the engine. This is the thermostat housing and the sensor is located next to it. It has a two-wire connector.
Start the engine and pull the connector off the top of the sensor. The fan should now operate. If the fan does not operate, replace the connector.
Check the cooling fan fuse in the fuse and relay box located on the driver's-side fender well. If the fuse is good, locate the cooling fan relay in the relay box. Pull the relay out of the box. There are four terminals on the relay. Relays always have a diagram on the side identifying the terminals. Connect the two jumper wires to the battery (B+) and the ground (-) terminals.
Touch one wire to the positive terminal on the battery and the other wire to the negative. Every time the wires contact the battery terminals, a discernible click can be heard and felt in the relay if it is good. If the relay works, the coolant temperature sensor has failed and needs to be replaced. If the relay fails, replace it.
