Analysis of Five Abnormal Phenomena of Engine Fans
Published time:
Sep 23,2021
① Check if the dual-temperature switch is malfunctioning. If it is damaged or malfunctioning, it should be replaced.
The fan only has high and low speeds
01
The fan motor can only operate at high or low speed.
02
Troubleshooting
① Check if the dual temperature switch is faulty. If it is damaged or malfunctioning, it should be replaced.
② The fan's second-gear relay is faulty; replace the fan relay.
③ The fan motor is faulty; repair or replace it.
④ Check the fan's control circuit for open circuits, short circuits, or poor contact.
Engine cooling fan runs continuously
See the table for troubleshooting and solutions for the engine cooling fan running continuously.
Table: Troubleshooting and Solutions
Engine cooling fan not turning
01
The engine coolant temperature is too high and boiling, but the cooling fan is not turning.
02
Troubleshooting
① Check the dual temperature switch (or coolant temperature sensor).
Disconnect the dual temperature switch plug and short-circuit the two terminals. If the fan works normally and the radiator coolant temperature reaches the normal operating temperature of the fan, the dual temperature switch is faulty and should be replaced; otherwise, there is a fault in other parts of the cooling system, and further inspection is required.
② Check the fan motor.
If the fan works normally when 12V DC voltage is directly applied to the two terminals of the fan motor, the fan motor is normal, and the fan control circuit fault should be ruled out; otherwise, the fan motor is faulty and should be replaced.
Idle instability
01
Idle instability manifests as engine shaking and uneven speed during idle operation. The causes include blockage of the idle air passage, malfunction of the idle device, weak spark from individual spark plugs, poor sealing of individual valves, air leakage in the intake manifold, too early or too late ignition timing, and improper idle adjustment.
02
Troubleshooting
When the engine is idling unsteadily, the idle speed should be adjusted first.
If the fault persists after idle speed adjustment, check whether the idle passage and idle air passage are blocked.
If the passage is blocked, clean it with gasoline and blow it through with compressed air.
If the passage is not blocked, stabilize the engine speed at a certain speed and listen for air leaks in the intake manifold and lower gasket. If air leaks occur, use tightening screws or adding/removing shims to eliminate them.
If idle instability is accompanied by a decrease in engine power, further check the spark plug operation, valve sealing performance, and ignition timing. Repair or adjust as necessary.
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