Chart C-12D Cooling Fan Check (No High Speed Fan)

Chart C-12D, Cooling Fan Check - No High Speed Fan:

A/C Head Pressure Switch Circuit:

*** This information has been updated according to Technical Service Bulletin #416507, dated April 1994.

CIRCUIT DESCRIPTION
Power for the fan motors comes from a 40A maxifuse element to terminal "30" on the relays. The relays are energized when current flows to ground through the PCM Quad-Driver #4. The left fan has two speeds and the right fan is a single speed fan.

Low Speed (Fan 1) Relay - The PCM energizes the relay through terminal "WD11" when engine coolant temperature reaches 100°C (212°F) or when A/C is requested.

High Speed (Fan 2) Relay - The high speed relay is energized by the PCM if the A/C head pressure switch opens, indicating refrigerant pressure above 210 psi (1448 kPa), or engine coolant temperature reaches 108°C (226°F).

TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
1. Test light should be "ON" because harness terminal "85" has B+ with ignition switch turned ON."
2. Jumpering harness terminals "30" and "87" bypasses the relay. If fan runs, the relay is faulty.
3. Checks CKT 473 back to the PCM. If CKT 473 is OK, it's a bad relay.