Chart C-12B Coolant Fan Control Circuit

Chart C-12B:

A/C Circuit:

CIRCUIT DESCRIPTION:
Power for the coolant fan motor comes through the fusible link to terminal "30" on the relay. The relay is energized when current flows to ground through the quad driver module inside the ECM.

Coolant fan Relay - The coolant fan relay is energized by the ECM. The ECM energizes the relay through terminal "YE8" when the coolant temperature reaches 100°C (212°F). The fan relay is also energized when A/C is requested.

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

1. The test light should be "ON" because the relay connector "85" terminal is fed directly from the ignition.

2. The scanner "MISC." test function allows manual control of the cooling fan relay. This test checks CKT 535 and the ECM.

3. Jumpering terminals "30" and "87" feeds the fan motor directly, and it should run.

4. Checks for battery feed at the cooling fan relay.