Engine Cooling Fan Buick Regal III

DESCRIPTION

Vehicle uses an electric cooling fan. The electric cooling fan is used for engine and A/C condenser cooling. Cooling fan operates when A/C is on and when engine coolant temperature exceeds a certain value.

OPERATION

All electric cooling fans operate when engine coolant temperature exceeds a certain value. 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 relay 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 Electronic Control Module (ECM) for fan control. When A/C control switch is on, and A/C system low pressure switch is closed, ECM receives a signal on this line and turns cooling fan on. The A/C compressor clutch does not have to engage for ECM to turn fan on.

On some models, the ECM may turn on fan relay and run fan for up to 7 minutes when engine is off. 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.

TROUBLE SHOOTING

Note. This article contains test charts which 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 articles in ENGINE PERFORMANCE Section

SCAN TESTER

A variety of information is transmitted through ALDL connector terminal "E" or "M" depending on engine. This data is transmitted at a high frequency which requires a Tech 1 Scan tester for interpretation. Several Scan testers are available for diagnostic work. Scan testers other than Tech 1 Scan tester will function and provide information for diagnostic work; however, some charts will specify a Tech 1 Scan tester. Failure to use a Tech 1 Scan tester when specified may result in incorrect diagnosis of a system.

Note. If a chart other than a C-10 or C-12 chart is referenced, see appropriate article in the ENGINE PERFORMANCE Section.

CHART C-12, COOLING FAN CIRCUIT DIAGNOSIS (2.5L)

Primary (No. 1) and secondary (No. 2) cooling fans are ECM controlled based on inputs from coolant temperature sensor, A/C control switches, vehicle speed and state of A/C compressor/engine cooling fan temperature switch. ECM controls cooling fans by grounding circuits No. 335 and/or No. 473, which energizes cooling fan relay(s). When cooling fans are energized, battery voltage is supplied to fan motors.

ECM grounds circuit No. 335 when coolant temperature is greater than 223°F (106°C) or when A/C has been requested. A/C compressor/engine cooling fan temperature switch opens with high A/C pressure, approximately 250 psi (17.6 kg/cm 2 ). ECM then grounds circuit No. 473 to energize secondary (No. 2) cooling fan relay. When ECM energizes either relay, ECM will keep fan relay on at least 60 seconds or until vehicle speed exceeds 70 MPH for fan No. 1 or 40 MPH for secondary (No. 2) fan. If Code 14 or 15 sets, ECM is in back-up mode: fan No. 1 will run at all times.

Note. Test numbers below refer to test numbers on diagnostic chart No. 1. (Scheme 2)

1. With diagnostic terminal grounded, cooling fan control driver(s) will close, which should energize fan relay(s).
2. If A/C compressor/engine cooling fan temperature switch or circuit is open, both fans would run whenever A/C is requested.
3. When A/C compressor/engine cooling fan temperature switch opens, secondary (No. 2) cooling fan relay is energized by ECM. Switch opens when A/C line pressure exceeds approximately 250 psi (17.6 kg/cm 2 ). NOTE: Test numbers below refer to test numbers on diagnostic chart No. 2. (Scheme 3)
4. B+ should be available to each relay when ignition is on.
5. Checks ability of ECM to ground circuits No. 335 and 473. SERVICE ENGINE SOON light should also be flashing at this point. If SERVICE ENGINE SOON light is not flashing, see DIAGNOSTIC CIRCUIT CHECK in BASIC TESTING article in the ENGINE PERFORMANCE Section.
6. If fan does not turn on at this point, circuit No. 702 and/or 532 is open or cooling fan motors are faulty.
7. A short to ground anywhere in battery feed circuit up to and including fan motor(s) may cause a blown fusible element.

Diagnostic Aids

If an overheating condition is suspected, verify if it is due to actual boilover. If gauge or light indicates an overheat condition and boilover is not evident, inspect gauge circuit for malfunction.

If vehicle is overheating and gauge or light indicates so but cooling fan is not coming on, check coolant sensor temperature using a Scan tester. Sensor may have shifted out of calibration and should be replaced. If engine is overheating and cooling fan is on, check cooling system.

Scheme 1

Scheme 2

Scheme 3

CHART C-10, A/C CLUTCH CONTROL CIRCUIT DIAGNOSIS (2.5L)

A/C clutch control is ECM controlled. ECM delays A/C clutch engagement approximately .4 second after A/C is turned on. This allows Idle Air Control (IAC) to adjust engine RPM before clutch engages. ECM also disengages A/C clutch during Wide Open Throttle (WOT), when high power steering pressure is present, or if engine is overheating. A/C clutch relay is energized when ECM provides a ground for circuit No. 459. A/C low pressure switch will open if A/C pressure is less than 40 psi (2.8 kg/cm 2 ). A/C high pressure switch will open if A/C pressure exceeds 440 psi (30.9 kg/cm 2 ). A/C compressor/engine cooling fan temperature switch (if equipped) opens when A/C pressure exceeds approximately 250 psi (17.6 kg/cm 2 ). Cooling fan No. 2 will then turn on.

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

1. ECM will only energize A/C relay when engine is running. Determines if relay or circuit No. 459 is faulty.
2. For clutch to properly engage, low pressure switch must be closed to provide battery voltage to relay. High pressure switch must be closed, so A/C request (B+) will be present at ECM.
3. Determines if signal is reaching ECM from circuit No. 66 from A/C control panel. Signal should only be present when A/C mode or defrost mode is selected.
4. Short to ground in any part of A/C request circuit could cause a blown fuse.
5. With engine idling and A/C on, ECM should ground circuit No. 459, which should cause test light to glow.

If complaint is insufficient cooling, problem may be an inoperative cooling fan No. 1 or 2 or A/C compressor/engine cooling fan temperature switch. Cooling fan No. 2 should engage when A/C pressure exceeds a value to open switch, which causes ECM to energize cooling fan relay No. 2. See CHART C-12 for cooling fan diagnosis. If fan operates correctly, check for a basic A/C problem.

Scheme 4

Scheme 5

CHART C-12, COOLING FAN CIRCUIT DIAGNOSIS (3.1L)

Cooling fan is ECM controlled based on inputs from coolant temperature sensor, A/C control switches, A/C pressure sensor and Vehicle Speed Sensor (VSS). ECM grounds circuits No. 335 and/or 473, energizing cooling fan relay(s) and turning on cooling fan(s). ECM grounds circuits No. 335 and/or 473 when coolant temperature is more than 223°F (106°C) or when A/C has been requested and A/C pressure is about 200 psi (14.1 kg/cm 2 ). When cooling fan is turned on, ECM will keep fan energized at least 60 seconds or until vehicle speed exceeds 70 MPH for fan No. 1 or 40 MPH for secondary (No. 2) fan. If Code 14 or 15 sets, ECM is in back-up mode; fan No. 1 will run continuously.

Note. Test numbers below refer to test numbers on diagnostic chart No. 1. (Scheme 7)

1. With diagnostic terminal grounded, cooling fan control driver(s) will close, which should energize cooling fan relay(s).
2. If A/C fan control switch or circuit is open, fan will run whenever A/C is requested.
3. With A/C clutch engaged, A/C fan control switch should open when A/C pressure exceeds approximately 200 psi (14.1 kg/cm 2 ). This signal should cause ECM to energize cooling fan relay(s). See C-10 chart in I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section.
4. Determines if A/C pressure sensor is faulty or if ECM or circuitry is faulty. NOTE: Test numbers below refer to test numbers on diagnostic chart No. 2. (Scheme 8)
5. B+ should be available to circuit No. 250 and terminal No. 2 of fan relay No. 1 when ignition is on.
6. Checks ability of ECM to ground circuits No. 335 and 473. SERVICE ENGINE SOON light should also be flashing at this point. If SERVICE ENGINE SOON light is not flashing, see DIAGNOSTIC CIRCUIT CHECK in BASIC TESTING article in the ENGINE PERFORMANCE Section.
7. If cooling fan does not run at this point, circuit No. 702 or 150 is open or cooling fan motor is faulty.

If an overheating condition is suspected, verify if it is due to actual boilover. If gauge or light indicates an overheat condition and boilover is not evident, inspect gauge circuit for malfunction.

If vehicle is overheating and gauge or light indicates so but cooling fan is not coming on, check coolant sensor temperature using a Tech 1 Scan tester. Sensor may have shifted out of calibration and should be replaced. If engine is overheating and cooling fan is on, check cooling system.

Scheme 6

Scheme 7

Scheme 8

CHART C-12, COOLING FAN CIRCUIT DIAGNOSIS (3.4L)

Cooling fan(s) are ECM controlled based on inputs from coolant temperature sensor, A/C control switch, Vehicle Speed Sensor (VSS) and A/C pressure sensor. ECM grounds circuits No. 335 and/or 473, energizing cooling fan relay(s) and turning on cooling fan(s). ECM grounds circuits No. 335 and/or 473 when coolant temperature is more than 223°F (106°C) or when A/C has been requested and A/C pressure is approximately 200 psi (14.1 kg/cm 2 ). When cooling fan is turned on, ECM will keep fan energized at least 30 seconds or until vehicle speed exceeds 70 MPH for cooling fan No. 1 (primary cooling fan) or 40 MPH for cooling fan No. 2 (secondary cooling fan). Also, if Code 14 or Code 15 is set or ECM is in fuel back-up mode, fan will run continuously.

Note. Test numbers below refer to test numbers on diagnostic chart No. 1. (Scheme 10)

1. With diagnostic terminal grounded, cooling fan control driver(s) will close, which should energize fan control relay(s).
2. If A/C pressure is more than 300 psi (21.1 kg/cm 2 ) or circuit is open, fan would run whenever A/C is requested.
3. With A/C clutch engaged and A/C pressure sensor functioning properly, fan should turn on when pressure exceeds approximately 200 psi (14.1 kg/cm(3)). This signal should cause ECM to energize fan control relay(s). See C-10 chart in I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section.
4. Determines if A/C pressure sensor is faulty or if ECM or circuitry is faulty. NOTE: Test numbers below refer to test numbers on diagnostic chart No. 2. (Scheme 11)
5. B+ should be available to circuits No. 250 and 1444 on relays when ignition is on.
6. Checks ability of ECM to ground circuits No. 335 and 473. SERVICE ENGINE SOON light should also be flashing at this point. If SERVICE ENGINE SOON light is not flashing, refer to DIAGNOSTIC CIRCUIT CHECK in BASIC TESTING article in the ENGINE PERFORMANCE Section.
7. If fan does not turn on, circuit No. 702, 532 or 150 is open or cooling fan motor(s) are faulty.

If an overheating condition is suspected, verify if it is due to actual boilover. If gauge or light indicates an overheat condition and boilover is not evident, inspect gauge circuit for malfunction.

If vehicle is overheating and gauge or light indicates so but cooling fan is not coming on, check coolant sensor temperature using a Tech 1 Scan tester. Sensor may have shifted out of calibration and should be replaced. If engine is overheating and cooling fan is on, check cooling system.

Scheme 9

Scheme 10

Scheme 11

CHART C-12A, COOLING FAN CIRCUIT DIAGNOSIS (3.8L)

ECM uses 3 relays to control 2 cooling fans. Both fans run at low speed when ECM energizes cooling fan relay "B" when coolant temperature exceeds 214°F (101°C) or when A/C is requested. With ignition off, ECM will operate cooling fans at low speed if coolant temperature exceeds 230°F (110°F) and intake air temperature exceeds 102°F (39°F) at time of key off. ECM will keep fans energized at low speed with key off for up to 2 minutes or until coolant temperature falls to less than 210°F (99°C).

Both fans run at high speed when ECM energizes all 3 relays with coolant temperature exceeding 226°F (108°C) or when A/C refrigerant pressure is more than 200 psi (14.1 kg/cm 2 ). Cooling fans will not run at high speed with ignition off.

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

1. Code 14 or 15 could mean cooling system or sensor is not operating normally; fan(s) operation cannot be checked correctly.
2. Selecting low speed fans under miscellaneous tests, fan control with Tech 1 Scan tester causes ECM to energize fan relay "B" and operates fans at low speed.
3. Selecting high speed fans under miscellaneous tests, fan control with Tech 1 Scan tester causes ECM to energize fan relays "B", "C", and "D", operating fans at high speed.
4. Cooling fans should run at low speed if an A/C mode is selected and ECM is receiving an A/C request signal.

If cooling fans operate normally but an overheat condition exists, see COOLANT TEMPERATURE-TO-RESISTANCE VALUES table in CODE 15 chart in appropriate TESTS W/CODES article in the ENGINE PERFORMANCE Section. Replace coolant temperature sensor if mis-scaled. If coolant temperature sensor is okay, check for basic cooling system problem.

If coolant temperature exceeds 230°F (110°C) and manifold air temperature exceeds 102°F (39°C) with ignition off, ECM will energize cooling fans at low speed for up to 2 minutes or until coolant temperature is less than 210°F (99°C).

Scheme 12

Scheme 13

CHART C-12B, NO LOW SPEED (3.8L)

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

Scheme 14

1. Test light on verifies B+ to harness terminals No. 2 and 3 with ignition on.
2. Test light on verifies wiring for both fans.
3. Test light on verifies circuit No. 702 between fan relay "D" and left side fan and circuit No. 533 between left side fan and fan relay "B".
4. Test light on verifies circuit 532 between fan relay "D" and right side fan and circuit No. 150 between right side fan and ground.

CHART C-12C-A, NO HIGH SPEED - RIGHT SIDE FAN (3.8L)

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

Scheme 15

1. Checks B+ and ignition at relay harness connector.
2. Test light on verifies circuit No. 536 to cooling fan relay "C".
3. Jumpering terminals No. 3 to 5 in relay "C" by-passes relay and should cause fan to run if fan, wiring and motor are okay.
4. Checks for B+ and ground to fan motor. Test light on at this point indicates a faulty fan motor connection or motor.

CHART C-12C-B, NO HIGH SPEED - LEFT SIDE FAN (3.8L)

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

Scheme 16

1. Checks ignition feed at relay "D" coil.
2. Ensures circuit No. 150 is not open between relay "D" and ground.
3. Isolates malfunction to ECM, wiring or fan relay "D".

CHART C-12D-A, LOW SPEED FAN(S) ON AT ALL TIMES (3.8L)

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

1. Low speed cooling fans may run for up to 2 minutes with ignition off.
2. Verifies proper ECM control of fans.
3. Checks circuit No. 535 shorted to ground or a faulty fan relay.
4. Checks for A/C request signal to ECM which would cause low speed fans operation.

If cooling fans operate normally but overheat condition exists, see COOLANT TEMPERATURE-TO-RESISTANCE VALUES table in CODE 14 chart in appropriate TESTS W/CODES article in the ENGINE PERFORMANCE Section. Replace coolant temperature sensor if mis-scaled. If coolant temperature sensor is okay, check for basic cooling system problem.

Scheme 17

CHART C-12D-B, HIGH SPEED FAN(S) ON AT ALL TIMES (3.8L)

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

1. Isolates problem to ECM control fault, faulty fan or relay or wiring problem.
2. Checks for proper operation of A/C head pressure switch.

If cooling fans operate normally but overheat condition exists, see COOLANT TEMPERATURE-TO-RESISTANCE VALUES table in CODE 14 chart in appropriate TESTS W/CODES article in the ENGINE PERFORMANCE Section. Replace coolant temperature sensor if mis-scaled. If coolant temperature sensor is okay, check for basic cooling system problem.

Scheme 18

Scheme 19

CHART C-10, A/C CLUTCH CONTROL CIRCUIT DIAGNOSIS (3.8L)

ECM controls A/C relay to delay A/C clutch engagement .4 second after A/C is turned on. This allows Idle Air Control (IAC) to adjust engine RPM before A/C clutch engages. ECM may apply A/C clutch during engine cranking to prevent A/C slugging. ECM also causes relay to disengage A/C clutch during Wide Open Throttle (WOT) operation. A/C relay is energized when ECM grounds circuit No. 366.

Note. Test numbers below refer to test numbers on diagnostic chart No. 1. (Scheme 21)

Scheme 20

Scheme 21

Scheme 22

Scheme 23

1. Compressor clutch should not engage with A/C off.
2. Checks operation of A/C cycling switch.
3. Checks if A/C request signal is getting to ECM through circuit No. 67. Test light off at this time indicates circuit No. 67 is open between cycling switch and ECM.
4. Checks for open circuits No. 66, 257, 750 or A/C control switch. NOTE: Test numbers below refer to test numbers on diagnostic chart No. 2. (Scheme 22)
5. Checks if ECM is controlling A/C clutch control relay.
6. Checks for battery voltage to A/C compressor relay through circuit No. 339.
7. By-passes relay to determine if problem is in relay, A/C clutch coil, circuit No. 59 or ground. NOTE: Test numbers below refer to test numbers on diagnostic chart No. 3. (Scheme 23)
8. A/C request on Tech 1 Scan tester should not display YES with A/C off.
9. Locates source of false A/C request signal.
10. Isolates A/C clutch from its control circuitry.
11. Determines whether a faulty relay or relay control circuit is causing clutch to not disengage.

Cooling Fan Circuit Wiring Diagram (2.5L, 3.1L & 3.4L). Scheme 24

Cooling Fan Circuit Wiring Diagram (3.8L). Scheme 25