Engine Cooling Fan - Electrical — Chevrolet Chevy Van G10 (1985-1995)

APPLICATION

Application	Engine
"G", "P", "R" & "V" Series	7.4L
"U" Body Lumina APV, Silhouette & Trans Sport	3.1L

ELECTRIC COOLING FAN APPLICATIONS

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. On all models except "G", "R" and "V" series trucks and vans, the ECM completes ground path for the cooling fan relay. Relay contacts then close and complete circuit between fusible link and fan motor. When the engine cools, the switch opens and fan stops. If coolant sensor fails, the ECM will command constant fan operation.

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.

On "G", "R" and "V" series trucks and vans, temperature sensor switch closes when a certain temperature has been reached. Relay contacts then close and complete circuit to the fan motor.

COOLING FAN RELAY LOCATION

Application	Location
"G" Series	Front Lower Relay At Left Side Of Cowl
"P" Series	Front Relay At Right Side Of Cowl Near Windshield Washer Bottle
"R" & "V" Series	Left Inner Fender Near Windshield Washer Bottle
"U" Series	Center Relay Located On Right Side Of Engine Compartment Behind The Headlight

COOLING FAN RELAY LOCATION

TROUBLE SHOOTING ("G", "P", "R", "V" SERIES)

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 appropriate article in ENGINE PERFORMANCE section.

Trouble shoot cooling fan problems through the use of cooling fan circuit diagram and system diagnosis procedures. (Scheme 1) For cooling fan relay location, see COOLING FAN RELAY LOCATION table.

Scheme 1

Scheme 1: TROUBLE SHOOTING ("G", "P", "R", "V" SERIES)

TROUBLE SHOOTING ("U" SERIES)

See CHART C-12, COOLING FAN CONTROL and (Scheme 2), (Scheme 3) and (Scheme 4) for cooling fan diagnosis. No other information available at time of publication.

CHART C-12, COOLING FAN CONTROL (3.1L - VIN D, "U" BODY)

The ECM controls cooling fan by inputs from coolant temperature sensor (located in front of distributor on left side of engine), A/C fan control switch, and vehicle speed. The ECM grounds the circuit to fan control relay which is the center relay located on right side of engine compartment behind the headlight. This energizes fan control relay for fan operation. Wiring circuit to fan control relay is grounded when coolant temperature exceeds 223°F (106°F) or when A/C is operating and A/C fan control switch opens with high A/C pressure of approximately 200 psi (14.1 kg/cm 2 ).

Note. Test numbers refer to test numbers on diagnostic charts.

With diagnostic terminal grounded, cooling fan driver closes and energizes fan control relay.
If A/C fan control switch or circuit is open, cooling fan operates whenever A/C is operating.
With A/C clutch energized, A/C fan control switch should open when A/C high pressure exceeds 200 psi (14.1 kg/cm 2 ). This signal indicates that ECM should energize fan control relay.
With ignition on, 12 volts should exist at terminals "A" and "D" of fan control relay.
This verifies ECM ability to ground the fan control relay. The "SERVICE ENGINE SOON" light should be flashing. If light fails to flash, check wiring circuit. See appropriate article in ENGINE PERFORMANCE section.
If cooling fan does not operate, open circuit exists between fan control relay or between A/C fan control switch and ground.

Diagnostic Aids

If an overheating condition is suspected, verify if this is due to actual boilover. If gauge or light indicates an overheat condition, and no boilover is in evidence, inspect the gauge/light circuit for malfunction.

If vehicle is overheating and the gauge or light indicates the same, but cooling fan is not operating, and "SCAN" tester indicates normal readings, coolant temperature sensor is out of calibration and should be replaced. If engine is overheating and cooling fan is on, check cooling system.