3.1L "W" Body (Lumina): Description

Power for fan motors is supplied through engine wiring harness junction block 1 and engine wiring harness junction block 2. Cooling fan relays are energized when current flows from MaxiFuse® 1 in engine wiring harness junction block 1 and FAN 3 fuse (25 amp) in engine wiring harness junction block 2 through relay coils to ground through Powertrain Control Module (PCM). Low speed fans control circuit is grounded for low speed fans operation. Low speed fans control circuit and high speed fans control circuits are all grounded for high speed fans operation.

During low speed fans operation, PCM supplies a ground path for fan control relay 1. This closes fan control relay 1 contacts, allowing current to flow from engine wiring harness junction block 1 through relay contacts to engine coolant fan motor 1. During low speed operation, ground path for engine coolant fan motor 1 is through fan control relay 2 and engine coolant fan motor 2. Result is a series circuit with both cooling fans running at low speed.

During high speed cooling fan operation, PCM supplies a ground path for fan control relay 1. PCM also supplies a ground path for fan control relay 2 and fan control relay 3. This closes all 3 cooling fan relays. During high speed fan operation, both right and the left engine cooling fans are supplied current from engine wiring harness junction block 1 and engine wiring harness junction block 2 and each cooling fan has its own ground path.