Part 4 of 4

Chart C-12D:

Wiring Diagram:

CIRCUIT DESCRIPTION:

Power for the fan motor comes through the fusible link to terminal "1" on all relays. The relays are energized when current flows to ground through the ECM (quad-drivers).

Low Speed Relay - The ECM energizes the relay through terminal "YC2" when the coolant temperature reaches 101°C (214°F). As long as the ignition remains in the "ON" position the coolant fan will continue to run until the coolant temperature falls below 99°C (210°F). The low speed fan will also run any time the A/C is requested.

High Speed Relay - The high speed relay is energized by the ECM or the A/C pressure switch. If the A/C refrigerant pressure reaches 275 psi (1896 kPa) or the coolant temperature reaches 108°C (226°F), the high speed fan relay is energized.

TEST DESCRIPTION: Numbers below refer to circled numbers on the diagnostic chart.

1. Test light should be "ON" because terminal "2" has B+ with ignition switch turned "ON."

2. Jumpering terminals "1" and "4" bypasses the relay, which should cause the fan to run. If it does the relay is at fault.

3. Checks circuit 536 back to the ECM. If circuit 536 is OK, it's a bad relay.

4. Checks wiring to the coolant fan motor. If OK, problem is connections or motor or motor ground.