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.
1986---87 OLDSMOBILE CALAIS & PONTIAC GRAND AM
SYSTEM DESCRIPTION
On 4 Cylinder models, the coolant fan is controlled by the Coolant Fan Relay. The Coolant Fan Temperature Switch closes when coolant temperature is high, providing a path to ground through the relay coil. The relay contacts close to apply battery voltage to the fan. On models with A/C, the coolant fan also operates when the compressor is ``On.'' The A/C Coolant Fan Relay is controlled by the Electronic Control Module (ECM). The ECM coil is supplied battery voltage through the A/C Mode Selector and the A/C Low Pressure Switch. The circuit is grounded through the ECM to the A/C coolant fan relay when the vehicle is traveling less than 35 mph. Its contacts close to ground the coolant fan relay coil. The fan is energized and its contacts apply battery voltage to the fan. On V6 models, a two speed heavy duty cooling fan is used which is controlled by cooling fan relays. During low speed operation, the low speed relay coil is grounded through the ECM or the low speed contacts of the A/C high pressure switch. The ECM grounds the coil when vehicle speed is less than 45 mph and engine coolant temperature exceeds 208 degrees F. The low speed contacts ground the coil of the coolant fan relay when there is high compressor pressure. With the low speed relay coil grounded, the associated contacts close and voltage is applied through the coolant fan resistor to the heavy duty coolant fan. The resistor drops part of the battery voltage and the fan operates at low speed. During high speed operation, the high speed relay coil is grounded through the high speed contacts in the A/C high pressure switch or the coolant fan temperature switch. The pressure switch high speed contacts close at refrigerant pressure higher than the pressure that closed the low speed contacts. The coolant fan temperature switch closes when coolant temperature reaches 228 degrees F.
SYSTEM CHECK
4 Cylinder Models
1. On models with A/C, start engine, then place A/C control selector in NORM position. Coolant fan should operate.
2. Return A/C control selector to OFF before engine warning lamp lights. Coolant fan should go ``Off.''
3. On all models, operate engine at fast idle for approximately ten minutes. Coolant fan should turn on before coolant temperature indicator comes on or gauge needle reaches H.
TROUBLESHOOTING
4 Cylinder Models
1. Check applicable A/C or Heater fuse, using a suitable fuse tester. Check fusible link F on Calais models.
2. If coolant fan does not operate at all, proceed as follows:
a. Remove coolant fan temperature switch, then connect a suitable jumper between dark green/white wire and ground and turn ignition switch ``On.'' If coolant fan does not operate, proceed to step b. If coolant fan operates and connections are satisfactory, replace coolant fan temperature switch.
b. With jumper in place, connect a suitable test lamp between red wire E and ground. Test lamp should light. Red wire E and dark green/white wire. Test lamp should light. Brown/white wire to dark green/white wire. Test lamp should light. If lamp lights in all cases, proceed to step c. If lamp does not light from E to ground, check fusible link F and red wire for open and repair as necessary. If lamp does not light from E to B, check dark green/white wire for open and repair as necessary. If lamp does not light from C to B, check brown/white wire, brown wire and connector C100 and repair as necessary.
c. Reconnect coolant fan temperature switch.
d. Move jumper between terminals E and A of coolant fan relay connector. If coolant fan operates, replace coolant fan relay. If coolant fan does not operate, proceed to step e.
e. With ignition switch ``Off'' and jumper installed, connect a suitable test lamp between black/red (B) wire and ground. Test lamp should light. Connect test lamp between black/red (B) wire and black (A) wire. Test lamp should light. If test lamp lights in both checks, replace coolant fan motor. If lamp does not light from B to ground, check black/red wire for open and repair as necessary. If lamp does not light from B to A, check black wire for open and repair as necessary.
f. Reconnect coolant fan relay and coolant fan connectors.
3. If coolant fan does not operate when A/C is selected, but operates when engine is hot, proceed as follows:
a. Start and idle engine, position A/C selector lever in NORM and if necessary, provide auxiliary floor fan, then connect test lamp between light blue/black wire (A) and ground. Test lamp should light. Connect test lamp between light blue/black wire (A) and light blue/black wire (C). Test lamp should light. Connect test lamp between light blue/black wire (A) and black wire (D). Test lamp should light. If all checks are satisfactory, proceed to step b. If test lamp does not light from A to ground, check light blue/black wire for open and repair as necessary. If lamp does not light from A to C, check light blue/black wire for open, repair as necessary, then check ECM for malfunction. If test lamp does not light from A to D, check black wire for open and repair as necessary.
b. Connect a fused jumper between terminals B and D of A/C coolant fan relay connector. If coolant fan operates, check connector or replace coolant fan Relay. If coolant fan does not operate, check dark green/white wire at S130.
c. Reconnect A/C coolant fan relay.
4. If coolant fan operates at all times with ignition ``On'' with engine cool and A/C ``Off,'' if equipped, proceed as follows:
a. Remove coolant fan temperature switch connector (dark green/white wire). If coolant fan stops, replace coolant fan temperature switch. If coolant fan does not stop, proceed to step b.
b. Remove coolant fan relay connector, then connect a suitable test lamp between terminal C (brown/white) to terminal B (dark green/white). If test lamp lights, check terminal B for ground. If test lamp does not light, replace coolant fan relay.