Radiator Cooling Fan Motor: Description and Operation

On models equipped with electric engine cooling fans, the battery ground cable should be disconnected whenever underhood service is performed.




V6-181 Engines
These vehicles use a 2-speed heavy duty cooling fan which is controlled by a cooling fan relay having 2 coils and 2 independent sets of contacts. During low speed cooling fan operation, the low speed relay is grounded through either the ECM or the low speed contacts of the A/C high pressure switch. The ECM grounds the coil when vehicle speed is less than 45 mph and the engine coolant is at normal operating temperature. The low speed contacts of the A/C high pressure switch close when high refrigerant pressure is present at the compressor. With the low speed relay coil grounded, the appropriate contacts close thus applying voltage through the cooling fan resistor to the cooling fan motor. The resistor drops part of the battery voltage so the fan runs at low speed. During high speed cooling fan operation, the high speed relay coil is grounded through the high speed contacts in the A/C high pressure switch or through the cooling fan temperature switch. The fan the runs at high speed.




V6-181
1. With engine cold and at idle, set A/C mode selector to NORM position and blower to HI position. Set temperature selector to COLD position. Leave vehicle doors open. Cooling fan should run first at low speed, then at high speed.
2. Set A/C mode selector to OFF position, and run engine at fast idle. After a few minutes, cooling fan should run at low speed. Cooling fan should run at high speed before coolant temperature indicator on instrument panel comes on.

TROUBLESHOOTING
1. On models with 4-151 engine, operate A/C blower to check fuse 22 on Calais; HTR-A/C fuse on Somerset.
2. On all models, visually check fuse 21 on Calais; ENG/FAN fuse on Somerset.
3. If cooling fan operates only with compressor on and not for hot engine, install new cooling fan temperature switch.
4. Connect a fused jumper wire from battery to cooling fan terminal B, blue/black wire on Calais; red/black wire on Somerset.
a. If fan runs, ECM diagnosis must be performed.
b. If fan does not run, check that black wire terminal E on Calais; terminal A on Somerset, is grounded. If ground is good, cooling fan is defective.

COOLING FAN, REPLACE
1. Disconnect battery ground cable.
2. Disconnect wiring from fan motor and frame.
3. Remove fan assembly from radiator support.
4. Reverse procedure to install.