APPLICATION
| Application | Engine |
|---|---|
| "G", "R" & "V" Series | 7.4L |
ELECTRIC COOLING FAN APPLICATIONS
Note. This article contains test charts that are part of General Motors Computerized Engine Controls. Only those charts required to test electric cooling fans are included. Other diagnostic codes may appear while performing electric cooling fan diagnosis. For complete information on General Motors Computerized Engine Control systems see COMPUTERIZED ENGINE CONTROL section.
DESCRIPTION
All FWD, and some RWD vehicles use an electric cooling fan. This fan is used for engine and A/C condenser cooling and operates when A/C is on and if engine overheats.
OPERATION
All electric cooling fans operate when engine coolant temperature exceeds a certain value. A/C equipped vehicles have a separate signal line to the ECM for fan control. When A/C control switch is "ON", and A/C system low pressure switch is closed, the ECM receives a signal on this line and turns on the cooling fan. The compressor clutch does not have to engage for ECM to turn fan on.
On some models, when engine is off, ECM may turn on the fan relay and run fan for up to 7 minutes. This occurs if hot conditions were present while engine was running. Hot conditions are based on Manifold Absolute Temperature (MAT) signal to ECM, coolant temperature and time from start.
Temperature sensor switch closes when a certain temperature has been reached. Relay contacts then close and completes circuit to the fan motor.
TROUBLE SHOOTING
Trouble shooting cooling fan problems through the use of cooling fan circuit diagram and system diagnosis procedures. (Scheme 1)
Note. See trouble shooting charts for passenger car cooling fan diagnosis.
