Engine Cooling Fan Oldsmobile Cutlass Ciera I

THERMOSTATICALLY CONTROLLED ELECTRIC COOLING FANS

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, see COMPUTERIZED ENGINE CONTROL article(s) in the COMPUTER CONTROLS section.

ELECTRIC COOLING FAN APPLICATIONS

DESCRIPTION

All FWD, and some other vehicles, use an electric cooling fan. This fan is used for engine and A/C condenser cooling, but fan only operates under certain conditions.

OPERATION

All electric cooling fans operate when engine coolant temperature exceeds a certain value. The ECM completes ground path for the winding of coolant 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.

A/C equipped vehicles have a separate signal line to the ECM for fan control. When A/C control switch is "ON" and the low pressure switch closed, the ECM receives a signal on this line and turns on the fan. The compressor clutch does not have to engage for ECM to turn fan on.

On some models, when engine is shutdown, 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 Air Temperature sensor (MAT), coolant temperature, and time from start.

TROUBLE SHOOTING

Note. Refer to COMPUTERIZED ENGINE CONTROLS article(s) in the COMPUTER CONTROLS section for more information.

Battery voltage is supplied to fan relay terminal "A", and from ignition, to terminal "D". Grounding relay terminal "F" will close relay and supply battery voltage to fan motor. Above 30 MPH, the ECM will remove ground from circuit No. 335. If coolant temperature and A/C pressure switches are open, fan will stop.

Fan is energized when

1. A/C is "on", and vehicle speed is less than 30 MPH.
2. Coolant temperature is greater than 226°F (108°C).
3. Code 14 or 15 is set.

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 the vehicle is overheating, and the gauge or light indicates the same, but the cooling fan is not coming on, check the coolant sensor temperature using a "scan" tester. The sensor may have shifted calibration. If the engine is overheating, and the cooling fan is on, the cooling system should be checked.

The cooling fan is totally controlled by the ECM based on inputs from the coolant sensor and fan control switch. The fan should run if coolant temperature is more than 226°F (108°C). Battery voltage is supplied to the fan relay on terminal "E", and ignition voltage to terminal "C".

Grounding circuit No. 335 (relay terminal "B") will energize the relay, and supply battery voltage to the fan motor. Once the fan relay is energized by the ECM, it will remain on for a minimum of 30 seconds.

The fan control switch mounted, in the A/C high pressure line, will open when head pressure exceeds 200 psi (14 kg/cm 2 ). This input causes the ECM to ground circuit No. 335. If a code 14 or 15 sets or the ECM is operating in the fuel back-up mode the ECM will turn on the cooling fan.

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

1. With diagnostic terminal grounded, cooling fan control driver will close, which should energize fan control relay.
2. If A/C fan control switch or circuit is open, the fan would run whenever A/C is requested.
3. With A/C clutch engaged, A/C fan control switch should open, when A/C pressure exceeds 200 psi (14 kg/cm 2 ).

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 the vehicle is overheating, and the gauge or light indicates the same, but the cooling fan is not coming on, check the coolant sensor temperature using a "Scan" tester. The sensor may have shifted calibration, and should be replaced. If the engine is overheating, and the cooling fan is on, the cooling system should be checked.

The cooling fan is totally controlled by the ECM based on inputs from the coolant sensor and fan control switch. The fan should run if coolant temperature is more than 226°F (108°C). Battery voltage is supplied to the fan relay on terminal "E", and ignition voltage to terminal "C".

Grounding circuit No. 335 (relay terminal "B") will energize the relay, and supply battery voltage to the fan motor. Once the fan relay is energized by the ECM, it will remain on for a minimum of 30 seconds.

The fan control switch mounted, in the A/C high pressure line, will open when head pressure exceeds 200 psi (14 kg/cm 2 ). This input causes the ECM to ground circuit No. 335. If a code 14 or 15 sets or the ECM is operating in the fuel back-up mode the ECM will turn on the cooling fan.

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

Scheme 1

1. Battery voltage should be available to both terminals "E" and "C" when ignition is on.
2. This test checks ability of the ECM to ground circuit No. 335. "Service Engine Soon" light should also be flashing at this point. If it isn't flashing, CEC system should be checked.
3. If fan does not turn on at this point, circuit No. 702 or circuit No. 150 is open, or cooling fan motor is faulty. (Scheme 1): Chart C-12, (2 of 2) Engine Cooling Fan 2.8L TPI

CHART C-12A, FAN CHECK 3.8L - VIN 3

On "VO8" (heavy duty cooling) system, 2 coolant fans are energized through one low speed, and 2 high speed, relays. On standard cooling applications, one fan and one low speed relay are used. Power for the fan motors comes through the fusible link to terminal No. 1 on all relays. The relays are energized when current flows to ground through the activation of the A/C, coolant switches, and/or the ECM.

1. Low Speed Relay The low speed relay is energized by the ECM or the A/C pressure fan switch. The ECM energizes the relay through terminal "D2" when the coolant temperature reaches 208°F (98°C) The low speed relay is also energized through the A/C pressure fan switch (terminal "B") when refrigerant pressure reaches 150 psi (10.5 kg/cm 2 ).
2. High Speed Relay The high speed relay is energized by the A/C high pressure fan switch and coolant temperature override switches. If the A/C refrigerant pressure reaches 275 psi (19 kg/cm 2 ), or the coolant temperature reaches 226°F (108°C), the high speed fan relay is energized. The ECM has no control of the high speed fan relay.
3. Optional High Speed Relay The optional high speed relay is energized by the A/C high pressure fan switch and coolant temperature override switch and/or the temperature switch. Relay is energized any time the standard high speed relay is energized. The ECM has no control of the optional high speed relay. NOTE: Test numbers refer to test numbers on diagnostic charts.

Scheme 2

1. Grounding the diagnostic test terminal should cause the ECM to ground circuit No. 535 and the fan should run in low speed.
2. Grounding the temperature switch harness terminal will check circuit No. 536 and the high side portion of the fan control relay.
3. This test separates and checks relay driver circuit and relay-to-fan circuit for open circuit or faulty relay.
4. This test checks to see if the temperature switch is grounding and is also grounded when the test light is on. The switch should close at 226°F (108°C).
5. The following steps will check the high pressure switches, and related wiring, from the switch to the fan control relay. If poor A/C performance is noted, the A/C pressure switches should be checked. The low speed fan should come on if high pressure exceeds 260 psi (18.3 kg/cm 2 ). (Scheme 2): Chart C-12A, Fan Check 3.8L - VIN 3

CHART C-12B, FAN CHECK - FAN ON AT ALL TIMES 3.8L - VIN 3

On "VO8" (heavy duty cooling) system, 2 coolant fans are energized through one low speed, and 2 high speed, relays. On standard cooling applications, one fan, and one low speed, relay is used. Power for the fan motors comes through the fusible link to terminal No. 1 on all relays. The relays are energized when current flows to ground through the activation of the A/C, coolant switches, and/or the ECM.

1. Low Speed Relay The low speed relay is energized by the ECM or the A/C pressure fan switch. The ECM energizes the relay through terminal "D2" when the coolant temperature reaches 208°F (98°C). The low speed relay is also energized through the A/C pressure fan switch (terminal "B") when refrigerant pressure reaches 150 psi (10.5 kg/cm 2 ).
2. High Speed Relay The high speed relay is energized by the A/C high pressure fan switch and coolant temperature override switches. If the A/C refrigerant pressure reaches 275 psi (19 kg/cm 2 ), or the coolant temperature reaches 226°F (108°C), the high speed fan relay is energized. The ECM has no control of the high speed fan relay.
3. Optional High Speed Relay The optional high speed relay is energized by the A/C high pressure fan switch and coolant temperature override switch and/or the temperature switch. Relay is energized any time the standard high speed relay is energized. The ECM has no control of the optional high speed relay. NOTE: Test numbers refer to test numbers on diagnostic charts.

Scheme 3

1. Checks to see if circuit No. 535 is shorted to ground. This would keep the relay grounded at all times.
2. Checks to see if circuit No. 536 is shorted to ground. A light indicates the wire is shorted to ground. The following tests will isolate the short.
3. If the test light is off after disconnecting ECM C-D connector, the ECM is shorted internally. Before replacing the ECM, be sure to check the resistance value of low speed side of the fan control relay. Replace if resistance is less than 20 ohms. Also, be sure the circuit No. 535 is not shorted to battery voltage. Check the resistance of the canister purge solenoid, and replace if under 20 ohms. (Scheme 3): Chart C-12B, Fan Check - Fan On At All Times 3.8L - VIN 3

CHART C-12C, FAN CHECK - NO LOW SPEED FAN 3.8L - VIN 3

On "VO8" (heavy duty cooling) system, 2 coolant fans are energized through one low speed, and 2 high speed, relays. On standard cooling applications, one fan, and one low speed, relay is used. Power for the fan motors comes through the fusible link to terminal No. 1 on all relays. The relays are energized when current flows to ground through the activation of the A/C, coolant switches, and/or the ECM.

1. Low Speed Relay The low speed relay is energized by the ECM or the A/C pressure fan switch. The ECM energizes the relay through terminal "D2" when the coolant temperature reaches 208°F (98°C). The low speed relay is also energized through the A/C pressure fan switch (terminal "B") when refrigerant pressure reaches 150 psi (10.5 kg/cm 2 ).
2. High speed relay The high speed relay is energized by the A/C high pressure fan switch and coolant temperature override switches. If the A/C refrigerant pressure reaches 275 psi (19 kg/cm 2 ), or the coolant temperature reaches 226°F (108°C), the high speed fan relay is energized. The ECM has no control of the high speed fan relay.
3. Optional High Speed Relay The optional high speed relay is energized by the A/C high pressure fan switch and coolant temperature override switch and/or the temperature switch. Relay is energized any time the standard high speed relay is energized. The ECM has no control of the optional high speed relay. NOTE: Test numbers refer to test numbers on diagnostic charts.

Scheme 4

1. Check for battery voltage at relay harness connector.
2. Jumpering terminals No.s 1 and 4 by-passes the relay. This should cause the fan to run, if fan motor, and wiring to the motor, are okay.
3. Grounding the test terminal should cause the ECM to ground circuit No. 535. At this point, the test light should light, if the ECM is okay and circuit No. 535 isn't open.
4. This checks for battery voltage and ground to the fan motor. If test light is on at this point, it indicates a faulty fan motor connection, motor connection, or motor. (Scheme 4): Chart C-12C, Fan Check - No Low Speed Fan 3.8L - VIN 3

Circuit Description

The coolant fan motor can be energized through two relays; a fan relay, or timer relay. Power for the coolant fan motor comes through the fusible link to both relays. The relays are energized when current flows to ground, through the activation of the A/C high pressure switch, temperature override switch, and/or the ECM.

Fan Relay

The fan relay is energized by the ECI, A/C high pressure switch and/or the temperature override switch. The ECI energizes the fan relay through terminal "D2", when coolant temperature reaches 98°C 208 F). The A/C high pressure switch energizes the fan relay when refrigerant pressure reaches 300 psi (2068 kPa).

Note. Numbers below refer to circled numbers on the diagnostic chart.

Scheme 5

Scheme 6

1. Checks to see if coolant fan motor runs at all times with ignition "ON".
2. Grounding the test terminal in the ALDL 5 connector, should cause the ECI to ground CKT 535. At this point, the coolant fan motor should run.
3. Grounding the temperature override switch harness to ground should cause the fan relay to turn "ON" the coolant fan motor. If the coolant fan motor runs, the fan relay and CKT 335 to the temperature override switch are good.
4. Grounding the A/C high pressure switch terminal should cause the fan relay to close, turning "ON" the coolant fan motor, proving the fan relay and circuit are OK.
5. Checks to see if the temperature override switch operates correctly. Test light should come "ON" at about 108° C (226° F), and the "hot light", on the instrument panel should come "ON" above 116° C (241° F).
6. Checks to see if the fan timer relay works. With temperature override switch harness grounded and ignition "OFF", fan should run until ground jumper is removed. (Scheme 5): Chart C12D, Schematic, Coolant Fan Check (A/C Equipped w/o Heavy Duty Cooling - 3.8L "A" Body) (Scheme 6): Flow Chart C12D, Coolant Fan Check (3.8L "A" Body, 1 of 3)

The coolant fan motor can be energized through two relays; a fan relay, or timer relay. Power for the coolant fan motor comes through the fusible link to both relays. The relays are energized when current flows to ground, through the activation of the A/C high pressure switch, temperature override switch, and/or the ECM.

The fan relay is energized by the ECI, A/C high pressure switch and/or the temperature override switch. The ECI energizes the fan relay through terminal "D2", when coolant temperature reaches 98°C 208 F). The A/C high pressure switch energizes the fan relay when refrigerant pressure reaches 300 psi (2068 kPa).

Note. Numbers below refer to circled numbers on the diagnostic chart.

Scheme 7

1. This check bypasses the fan relay and applies B+ directly to the coolant fan motor through CKT 532. At this point, the coolant fan motor should run.
2. Checks to see if problem is the fan relay, wiring, or ECM.
3. Checks for presence of B+ to relay connector terminal "5".
4. Checks for presence of B+ to relay connector terminal "A".
5. Checks for an open ground or coolant fan motor circuit, then checks for an open in CKT 532, between fan relay and coolant fan motor or faulty coolant fan motor. see scheme 9: Chart C12E, Schematic, Coolant Fan Check (A/C Equipped w/o Heavy Duty Cooling - 3.8L "A" Body) (Scheme 7): Flow Chart C12E, Coolant Fan Check (3.8L "A" Body, 2 of 3)

The coolant fan motor can be energized through two relays; a fan relay, or timer relay. Power for the coolant fan motor comes through the fusible link to both relays. The relays are energized when current flows to ground, through the activation of the A/C high pressure switch, temperature override switch, and/or the ECM.

The fan relay is energized by the ECI, A/C high pressure switch and/or the temperature override switch. The ECI energizes the fan relay through terminal "D2", when coolant temperature reaches 98°C 208 F). The A/C high pressure switch energizes the fan relay when refrigerant pressure reaches 300 psi (2068 kPa).

Note. Numbers below refer to circled numbers on the diagnostic chart.

Scheme 8

1. Checks for B+ at terminals "1" and "4" to the timer relay.
2. Checks to be sure CKT 639 does not have voltage when the ignition switch is "OFF". If CKT 639 has voltage, with the ignition "OFF", the timer relay will not turn the fan "ON".
3. Checks to be sure CKT 450 is a good ground. see scheme 11: Chart C12F, Schematic, Coolant Fan Check (A/C Equipped w/o Heavy Duty Cooling - 3.8L "A" Body) (Scheme 8): Flow Chart C12F, Coolant Fan Check (3.8L "A" Body, 3 of 3)

The coolant fan motor can be energized through two relays; a fan relay, or timer relay. Power for the coolant fan motor comes through the fusible link to both relays. The relays are energized when current flows to ground, through the activation of the A/C high pressure switch, temperature override switch, and/or the ECM.

The fan relay is energized by the ECI, A/C high pressure switch and/or the temperature override switch. The ECI energizes the fan relay through terminal "D2", when coolant temperature reaches 98°C 208 F). The A/C high pressure switch energizes the fan relay when refrigerant pressure reaches 300 psi (2068 kPa).

Note. Numbers below refer to circled numbers on the diagnostic chart.

Scheme 9

1. This step will separate the problem as either the timer relay or the fan relay.
2. Checks for short to voltage in CKT 532.
3. Checks to see if CKT 535 is shorted to ground, which would keep the relay grounded at all times.
4. Checks to see if CKT 335 is shorted to ground. A light indicates the wire is shorted to ground and following the steps will isolate the short.
5. If the test light is "OFF" after disconnecting, the ECM is shorted internally. see scheme 13: Chart C12G, Schematic, Coolant Fan On At All Times (A/C Equipped w/o Heavy Duty Cooling - 3.8L "A" Body) (Scheme 9): Flow Chart C12G, Coolant Fan On At All Times (3.8L "A" Body)

On VO8 (heavy duty cooling) systems, the standard coolant fan motor and the VO8 fan motor are energized through a coolant fan relay and a VO8 fan relay and/or a coolant fan timer relay. Power for the coolant fan motors come through the fusible link to all relays. The relays are energized when current flows to ground through the activation of the A/C high pressure switch, temperature override switch and/or the ECM.

Coolant Fan Relay

The coolant fan relay is energized by the temperature override switch, A/C high pressure switch and/or the ECM. The ECM energizes the coolant fan relay through terminal "D2" when the coolant temperature reaches 98° C (208° F), and vehicle speed is below 45 mph. The relay is also energized through terminal "B" of the A/C high pressure switch (150 psi) and/or the temperature override switch (108°C).

VO8 Fan Relay

The pusher fan is installed as part of the heavy duty cooling package (VO8) and is turned "ON" when A/C system pressure reaches 275 psi (1896 kPa) or coolant temperature reaches 108° C (226° F).

The coolant ran relay is energized by the temperature override switch. If the coolant temperature is 108° C (226° F) or higher when the ignition switch is turned "OFF", the timer relay is energized for 10 minutes or until the coolant temperature is lowered below 108° C (226° F). The standard coolant fan is the only fan that will run with the ignition switch "OFF".

Note. Numbers below refer to circled numbers on the diagnostic chart.

Scheme 10

Scheme 11

1. Checks to see if fans run at all times with ignition "ON".
2. Grounding the test terminal, in the ALDL connector, should cause the ECM to ground CKT 535. At this point, the standard coolant fan should run.
3. Grounding the temperature override switch harness to ground should cause the relays to turn "ON" both fans. If the fans run, the fan control relays and CKT 335 to the temperature override switch are good.
4. Grounding each pressure switch terminal should cause relays to close, turning "ON" fans, proving relays and circuits are OK.
5. Checks to see if temperature override switch operates correctly. Test light should come "ON" at about 108° C (226° F), and the "hot light" on the instrument panel should come "ON" above 116° C(241° F).
6. Checks to see if coolant fan relay works. With temperature override switch harness grounded, the coolant fan motor should run until ground jumper is removed. (Scheme 10): Chart C12H, Schematic, Coolant Fan Check (A/C Equipped w/Heavy Duty Cooling - 3.8L "A" Body) (Scheme 11): Flow Chart C12H, Coolant Fan Check (3.8L "A" Body, 1 of 3)

On VO8 (heavy duty cooling) systems, the standard coolant fan motor and the VO8 fan motor are energized through a coolant fan relay and a VO8 fan relay and/or a coolant fan timer relay. Power for the coolant fan motors come through the fusible link to all relays. The relays are energized when current flows to ground through the activation of the A/C high pressure switch, temperature override switch and/or the ECM.

The coolant fan relay is energized by the temperature override switch, A/C high pressure switch and/or the ECM. The ECM energizes the coolant fan relay through terminal "D2" when the coolant temperature reaches 98° C (208° F), and vehicle speed is below 45 mph. The relay is also energized through terminal "B" of the A/C high pressure switch (150 psi) and/or the temperature override switch (108°C).

The pusher fan is installed as part of the heavy duty cooling package (VO8) and is turned "ON" when A/C system pressure reaches 275 psi (1896 kPa) or coolant temperature reaches 108° C (226° F).

The coolant ran relay is energized by the temperature override switch. If the coolant temperature is 108° C (226° F) or higher when the ignition switch is turned "OFF", the timer relay is energized for 10 minutes or until the coolant temperature is lowered below 108° C (226° F). The standard coolant fan is the only fan that will run with the ignition switch "OFF".

Note. Numbers below refer to circled numbers on the diagnostic chart.

Scheme 12

1. This check bypasses the coolant fan relay and applies B+ to the coolant fan motor through CKT 532. At this point, the fan should run.
2. Checks to see if problem is the coolant fan relay, wiring, or ECM.
3. Checks for presence of ignition voltage to relay connector terminal "5".
4. Checks for presence of B+ to coolant fan relay connector terminal "A".
5. Checks for an open ground or fan motor circuit, then checks for an open in CKT 532, between coolant fan relay and motor, or faulty motor. see scheme 17: Chart C12I, Schematic, Coolant Fan Check (A/C Equipped w/Heavy Duty Cooling - 3.8L "A" Body) (Scheme 12): Flow Chart C12I, Coolant Fan Check (3.8L "A" Body, 2 of 3)

On VO8 (heavy duty cooling) systems, the standard coolant fan motor and the VO8 fan motor are energized through a coolant fan relay and a VO8 fan relay and/or a coolant fan timer relay. Power for the coolant fan motors come through the fusible link to all relays. The relays are energized when current flows to ground through the activation of the A/C high pressure switch, temperature override switch and/or the ECM.

The coolant fan relay is energized by the temperature override switch, A/C high pressure switch and/or the ECM. The ECM energizes the coolant fan relay through terminal "D2" when the coolant temperature reaches 98° C (208° F), and vehicle speed is below 45 mph. The relay is also energized through terminal "B" of the A/C high pressure switch (150 psi) and/or the temperature override switch (108°C).

The pusher fan is installed as part of the heavy duty cooling package (VO8) and is turned "ON" when A/C system pressure reaches 275 psi (1896 kPa) or coolant temperature reaches 108° C (226° F).

The coolant ran relay is energized by the temperature override switch. If the coolant temperature is 108° C (226° F) or higher when the ignition switch is turned "OFF", the timer relay is energized for 10 minutes or until the coolant temperature is lowered below 108° C (226° F). The standard coolant fan is the only fan that will run with the ignition switch "OFF".

Note. Numbers below refer to circled numbers on the diagnostic chart.

Scheme 13

1. Checks to be sure constant B+ is at terminals "1" and "4" to the timer relay.
2. Checks to be sure CKT 639 does not have voltage when the ignition switch is "OFF". If CKT 639 has voltage, with the ignition "OFF", the timer relay will not turn the fan "ON".
3. Checks to be sure CKT 450 is a good ground. see scheme 19: Chart C12J, Schematic, Coolant Fan Check (A/C Equipped w/Heavy Duty Cooling - 3.8L "A" Body) (Scheme 13): Flow Chart C12J, Coolant Fan Check (3.8L "A" Body, 3 of 3)

On VO8 (heavy duty cooling) systems, the standard coolant fan motor and the VO8 fan motor are energized through a coolant fan relay and a VO8 fan relay and/or a coolant fan timer relay. Power for the coolant fan motors come through the fusible link to all relays. The relays are energized when current flows to ground through the activation of the A/C high pressure switch, temperature override switch and/or the ECM.

The coolant fan relay is energized by the temperature override switch, A/C high pressure switch and/or the ECM. The ECM energizes the coolant fan relay through terminal "D2" when the coolant temperature reaches 98° C (208° F), and vehicle speed is below 45 mph. The relay is also energized through terminal "B" of the A/C high pressure switch (150 psi) and/or the temperature override switch (108°C).

The pusher fan is installed as part of the heavy duty cooling package (VO8) and is turned "ON" when A/C system pressure reaches 275 psi (1896 kPa) or coolant temperature reaches 108° C (226° F).

The coolant ran relay is energized by the temperature override switch. If the coolant temperature is 108° C (226° F) or higher when the ignition switch is turned "OFF", the timer relay is energized for 10 minutes or until the coolant temperature is lowered below 108° C (226° F). The standard coolant fan is the only fan that will run with the ignition switch "OFF".

Note. Numbers below refer to circled numbers on the diagnostic chart.

Scheme 14

1. This step will separate the problem between the coolant fan timer relay or the coolant fan relay.
2. Checks for short to voltage in CKT 532 or 533.
3. Checks to see if CKT 335 or 535 is shorted to ground, which would keep the coolant fan relay grounded at all times.
4. Checks to see if CKT 335 is shorted to ground. A light indicates the wire is shorted to ground and the following steps will isolate the short.
5. If the test light is "OFF" after disconnecting, the ECM is shorted internally. see scheme 21: Chart C12K, Schematic, Coolant Fan Check (A/C Equipped w/Heavy Duty Cooling - 3.8L "A" Body) (Scheme 14): Flow Chart C12K, Coolant Fan On At All Times (3.8L "A" Body)

This unit is a flexible blade assembly designed to flex blades as engine RPM increases. As RPM increases, blade pitch decreases, thereby saving power and decreasing noise level. Keep fan belt adjusted to proper tension as necessary. (Scheme 15)

Flex Blade Fan Assembly. Scheme 15

Most air conditioned models use a thermostatically controlled fluid fan and torque control clutch. Thermal control drive is a silicone-filled coupling connecting fan to a fan pulley, and is operated by a control valve. The Control valve is operated by a temperature sensitive bi-metallic coil (or strip) and controls flow of silicone through the clutch.

During periods of operation when radiator discharge air temperature is low, fan clutch speeds are slowed, decreasing load on fan belt. High radiator discharge air temperature causes bi-metallic coil or strip to allow a greater flow of silicone to enter clutch. This increases drag between driven member and driving member resulting in a higher fan speed and increased cooling.

Thermostatically Controlled Fan Assembly. Scheme 16

Note. Shown with stamped face and bi-metal coil spring.

TESTING

1. In cases of engine overheating or insufficient air conditioning start with a cool engine to ensure complete fan clutch disengagement. Cover radiator grille sufficiently to induce high engine temperature.
2. Start engine and operate at 2000 RPM. Turn on air conditioning (if equipped). A fan roar will be noticed when fan clutch engages. NOTE: It takes approximately 5-10 minutes for temperature to become hot enough to allow engagement of fan clutch. While operating engine under this condition, observe temperature light or gauge to prevent overheating. If car overheats, remove cover from radiator grille.
3. When clutch engages, remove radiator grille cover and turn A/C off to assist in engine cooling. After several minutes fan clutch should disengage. This can be determined by a reduction in fan speed and roar. If fan fails to function as described, it should be replaced.