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Nie, dziękuję Przekieruj mnie tamwhat are causes of car engine fun not turning on
‐ The engine (radiator) fan stays off when the electrical supply, the control signal or the motor itself is interrupted.
‐ Typical culprits: blown fuse, faulty relay, open-circuit or shorted wiring/ground, defective coolant-temperature sensor / thermo-switch, failed fan-control module or ECU driver, seized or burnt-out fan motor, mechanical obstruction, or—in belt-driven systems—a bad fan clutch.
System architecture
• Modern cars use an electric, brush- or brushless-DC fan commanded by the ECU/FCM through a relay or a smart MOSFET/PWM driver. Older cars may rely on a two- or three-pin thermo-switch in the radiator.
• Activation paths
– Stage 1: Low-speed (≈20–25 A) triggered at ~95 °C or when A/C is ON.
– Stage 2: High-speed (≈30–40 A) triggered at ~105 °C or by high A/C-condenser pressure.
Root-cause groups
a. Power delivery
‑ High-current fuse (30–50 A) open; low-current (5–10 A) control-side fuse open.
‑ Corroded or loose battery +B feed, chassis ground, or fan-ground eyelet; >0.5 V drop stalls the motor.
b. Switching element
‑ Relay contacts carbonised/pitted or coil open-circuit (Ω→∞).
‑ Solid-state driver MOSFET shorted (fan runs continuously) or open (fan never starts).
c. Sensing & logic
‑ Coolant-temperature sensor (CTS) out of range; e.g. stuck at –40 °C (open) or 140 °C (short).
‑ Radiator thermo-switch stuck open.
‑ ECU/FCM firmware corruption, internal transistor failure or CAN bus fault (newer vehicles).
d. Actuator
‑ Motor brushes worn, commutator burnt, winding open/short, bearings seized.
‑ Mechanical blockage: leaves, plastic bags, broken shroud, mis-shaped blade.
e. Auxiliary factors
‑ Low coolant => sensor not submerged => no “hot” reading.
‑ Stuck-open thermostat keeps coolant ≤85 °C; fan never receives “ON” command.
Electrical theory
Fan current \(I ≈ P/V\). With a 120 W fan on a 13.5 V bus, \(I≈9 A\) at low speed (PWM 40 %), \(I≈18 A\) at full duty. Supply wiring, relay contacts and fuses must be sized accordingly; 10 mΩ of extra resistance causes a 0.18 V drop and ~1.6 W dissipation at 18 A—enough to melt a marginal crimp in minutes.
Practical manifestations
• Fan runs with A/C but not on temperature → suspect CTS / thermo-switch / ECU logic.
• No fan in any mode, fuse good → suspect relay, wiring, ground.
• 12 V present at fan connector but no motion → seized motor.
• Intermittent fan, especially after puddles → water-intrusion in relay box or FCM.
‐ Since ≈2015 many OEMs moved to brushless fans with integrated PWM drivers controlled by LIN or CAN (e.g. VW 5Q0959455). Failure modes shift from relay to driver electronics; diagnostics requires a scan tool capable of sending a 25 kHz/11–90 % duty request.
‐ Some hybrids/EVs employ variable-speed cooling modules that ramp from 10 % to 100 %, so fuse blowing is rarer but LIN checksum errors become common DTCs (e.g. P0C73).
‐ Right-to-Repair regulations (EU 2023/607) oblige manufacturers to provide pin-outs and duty cycle tables, easing independent diagnostics.
Example: VW Polo 6N2 (1999-2002)
• Fuse S5 = 30 A motor feed (engine-bay box).
• Relay J293 (position 2/relief panel) for low speed; high-speed path via Fan-Control-Unit under battery.
• Radiator thermo-switch F18 pins: 1=Red/White (low), 2=Red (12 V), 3=Red/Black (high). Bridging 2→1 or 2→3 forces respective speeds—quick isolation test.
Voltage-drop test procedure
‐ Overheating due to an inoperative fan can cause engine failure and endanger occupants; ignoring the fault may violate road-worthiness regulations (e.g. UK MOT Section 7.1).
‐ Bypassing fuses with oversized ratings or hard-wiring the fan can lead to wire fires—potential criminal negligence.
‐ Always disconnect the battery negative before high-current tests; spinning fan blades constitute a laceration hazard.
Potential challenges & mitigation
‐ Intermittent faults: use thermal camera to spot hot fuses/relays.
‐ Limited access: on transverse engines, remove upper radiator cover for fan connector reach.
‐ Water ingress: apply dielectric grease to connectors after repair.
‐ Exact pin-outs, fuse numbers and activation temperatures vary by make/model; always consult the service manual.
‐ Some ECUs delay fan run-on after key-off; absence of post-shut fan noise is not conclusive.
‐ Impact of brushless fan PWM frequency on EMC compliance.
‐ Predictive cooling using CAN-bus thermal models in EV platforms.
‐ Condition-based maintenance via motor current signature analysis.
A non-operational engine fan is almost always the result of a break in the power-supply chain, a failed control element, or a defective motor. Start with simple visual and fuse checks, progress through relay and wiring tests, and finish with sensor/ECU diagnostics. Modern vehicles increasingly use smart brushless systems, so scan-tool and PWM/LIN analysis skills are becoming essential. Address the issue promptly to avoid overheating, costly engine damage and potential safety liabilities.
