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Autopapyrus · Toyota Corona 3S-FE 2.0 (1997)
https://autopapyrus.com/guides/toyota/corona/diagnosing-a-cooling-fan-that-does-not-run/
Compiled automatically from service literature and owner experience. Specs are for the typical configuration — check them against your exact car before you start.

Toyota Corona 3S-FE 2.0 (1997): Diagnosing a Cooling Fan That Does Not Run

The cooling fan on the 3S-FE engine is controlled through the ECU based on the signal from the coolant temperature sensor. Typical causes of failure are a faulty fan switch sensor, a burned-out relay, a blown fuse, broken wiring, or a failed fan motor. Diagnosis is done by checking each element of the circuit in sequence.

Difficulty: Medium Time: 1-2 hours Steps: 8 Tools: multimeter, 12 V test light, screwdriver, jumper wire, 10 mm wrench

Part

  • 🔩 depending on the fault found: fuse, fan relay, fan switch temperature sensor, fan motor
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Step by step

8 steps
  1. Open the hood, start the engine, and turn the A/C on to maximum. If the fan starts, the A/C system is working and the problem is in the temperature sensor circuit or the cooling relay. If it does not start, move on to checking the power supply.
  2. Find the fuse and relay box in the engine compartment (usually on the right or left near the fender). The cover has a layout diagram. Find the CDS FAN and RDI FAN fuses (the labels may differ, so look for FAN or COOLING). Remove the fuse and inspect the element. If it is burned out, replace it with one of the same rating (usually 30-40 A). If the new fuse blows right away, there is a short circuit in the wiring and the circuit needs a detailed check.
  3. Find the fan relay in the same box (FAN No.1 or FAN RELAY). Remove the relay and inspect the contacts for oxidation or melting. Replace it with a known-good relay of the same type, or bridge the corresponding terminals in the relay socket with a jumper wire. If the fan runs, the relay is faulty.
  4. Check for power at the fan motor directly. Disconnect the connector from the fan motor (usually near the radiator). With the engine hot (coolant temperature above 95 °C (203 °F)), use a multimeter to check for 12 V. If there is no voltage, the problem is in the temperature sensor or the ECU. If there is voltage but the fan does not spin, the motor is faulty.
  5. To test the fan motor, connect it directly to the battery with jumper wires (positive and negative). If the motor runs, the problem is in the control circuit (relay, sensor, wiring). If it does not run, replace the fan motor.
  6. Check the fan switch sensor. On the 3S-FE engine, the sensor is not on the radiator. It is on a three-way fitting near the cylinder head, where three temperature sensors are installed: one for the instrument cluster, one for the ECU, and one for the fan switch. Disconnect the connector from the fan switch sensor and bridge the terminals in the wiring harness connector with a jumper wire. If the fan comes on, the sensor is faulty and must be replaced.
  7. Inspect the wiring from the relay box to the fan for kinks, melted insulation, and oxidized connectors. Pay special attention to the ground points (negative wires to the body). Clean the contacts of corrosion and tighten the mounting.
  8. If all the elements are good but the fan still does not switch on automatically, the ECU may be faulty, or there may be a break in the signal circuit from the temperature sensor to the control unit. Check the wiring for continuity with a multimeter in continuity mode.

Common mistakes and warnings

  • Do not drive the car with a non-working fan in city traffic or stop-and-go conditions. Engine overheating will warp the cylinder head and blow the head gasket. When the A/C is turned on, the fan should run regardless of engine temperature. If it does not, also check the A/C system (pressure switch, receiver-drier connector).