Symptom: After a 1992 Toyota Camry 3.0 L annual car owner to reflect the engine start, the radiator fan always rotates at high gear.
Check Analysis: take the car, I first open the engine compartment lid, start the engine, radiator fan rotates at high speed immediately. After a period of operation of the engine, the hand feels hot water radiator touch, touch feeling hot downcomer. Is not result in clogged radiator coolant temperature is too high, the radiator fan rotates at high speed it? After that ask customers for troubleshooting purposes, the car had just cleaned the radiator and replace through the radiator, but the water temperature difference between the upper and lower still larger. In this case, we can rule out the possibility of a problem with the radiator. Infrared thermometer with a coolant temperature of the engine of measurement, I found that the temperature is not high, and the customer is always in the water table to reflect a lower position, so I confirmed radiator fan is always rotated at high speed cause the thermostat does not open, so the heat on water and under the water’s temperature difference is large.
Next, to find the reason for high-speed rotation of the radiator fan. The engine radiator is equipped with a hydraulic system controlled by an electronic fan. A hydraulic pump driven by rotation of the engine, the radiator fan rotated by the hydraulic motor driven by hydraulic oil. Radiator fan control unit inputs the engine speed signal, an idle signal of a throttle position sensor, engine coolant temperature signal and the air conditioner operation signal to achieve control of the cooling fan by a hydraulic oil flow speed solenoid valve control oil flow. Thus informed, the vehicle includes a hydraulic pump to be checked parts, radiator fan hydraulic motor, a hydraulic oil line, and radiator fan speed control system.
The author believes that the analysis, since the radiator fan is rotatable high speed, this indicates a hydraulic pump, hydraulic motor and a radiator fan hydraulic line largely intact, the problem should be the speed control in the radiator fan system. With a lift vehicle lift, locate and hydraulic pump oil flow control valve, the hydraulic fluid flow control disconnect the plug valve in the lower front of the engine, the radiator fan stopped turning the results, indicating that the hydraulic fluid flow control valve is normal. Lowering the vehicle, found at the engine coolant temperature sensor front end of the upper portion of the engine, coolant temperature sensor plug 2 is stripped of the sheath wire small mouth 2, it should be stripped during the previous service personnel check. In the measurement with a multimeter at cold peelBut the resistance value of the liquid temperature sensor, and to find the service manual temperature value corresponding to the same query results with actual water temperature of the engine coolant temperature sensor indicating normal. The two legs are connected to the pilot light conductors 2 of the coolant temperature sensor, the pilot light will do so with integrated coolant temperature sensor resistance becomes smaller, the engine coolant temperature is equivalent to the increase, the result radiator fan turn faster, and this shows the coolant temperature sensor, the hydraulic oil flow control valve and a hydraulic fan control unit largely intact. I asked the owner to hydraulic fan control unit dashboard lower right, before that service personnel had been overhauled this control unit and associated wiring harness checked, but found no abnormalities. Because the check hydraulic fan control unit and associated wiring harness much trouble, so I decided to check other components.
view the circuit diagram, the author found that a high-pressure air-conditioning fan switch is also connected to a hydraulic control unit. Found in the engine compartment front left air conditioning high pressure switch, ask the owner, the owner said, this air-pressure switch is not checked. Disconnect the connection plug and conditioned by high voltage switch shorting jumper, an air conditioning system which is equivalent to a normal pressure (air conditioner pressure switch disconnect only if the plug, the air conditioning system is equivalent to the pressure is too high, i.e. the refrigerant in the air conditioning pipes high temperature), and found that the radiator fan speed decreases, a period of time after the engine idling, the engine temperature is gradually increased to normal operating temperature.
Troubleshooting: check the air conditioning system, car air-conditioning system is not found to work, but no air conditioning refrigerant lines. Ask the customer, the customer said that because of the previous winter, so they did not use air conditioning, so I advise clients on the air conditioning system refrigerant leak and filling. After filling the refrigerant, engine radiator fan is working properly.
reviewed: Review cause of the failure of the car, because no refrigerant in the air conditioning pipe, so that the high-pressure air-conditioning switch is always in the OFF state, the control unit hydraulic fan mistaken the high pressure air conditioner refrigerant line , i.e. the temperature of the refrigerant in the air conditioning pipe is too high, high-speed rotation to thereby control the radiator fan, causing the air conditioner condenser heat sink means can not be raised together, affect the operation of the engine. In fact, before maintenance personnel have checked the number of related components, but probably because there is no reason to check the circuit diagram without air conditioning high pressure switch, which led to take a detour to find the cause. Yan Wei
(Yan K)