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.




1985---87 CADILLAC CIMARRON

SYSTEM DESCRIPTION
The cooling fan is controlled by the cooling fan relay whose contacts have voltage available at all times. The relay coil has voltage through the C-H fuse when ignition switch is in RUN position. The cooling fan relay is activated by any of the following conditions:
a. When engine coolant temperature exceeds 234 degrees F, coolant temperature sender signals ECM. The ECM in turn activates cooling fan relay which receives voltage through C-H fuse. The cooling fan relay contacts close, allowing current to flow through fusible link C and operate cooling fan.
b. On 4-121 VIN P engine, ECM will activate cooling fan relay when A/C is on and vehicle speed is below 40 mph. With vehicle speed above 40 mph, engine temperature determines operation of cooling fan relay. When A/C is off, and vehicle speed is above 40 mph, ECM will deactivate cooling fan relay at 225 degrees F.
c. On V6-173 VIN W engine, ECM activates cooling fan relay when A/C high side pressure exceeds 240 psi.

TROUBLESHOOTING
Cooling Fan Does Not Run
1. Check C-H fuse.
2. Check fusible link C.
3. Check cooling fan relay by listening for click when grounding dark green/white wire at cooling fan relay.
Cooling Fan Runs Constantly With Ignition Switch In RUN
1. Check cooling fan relay.
2. Disconnect dark green/white wire at cooling fan relay. If fan stops, check ECM.

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.