Failure phenomenon: a red CA7220E car, mileage 450000 km, users find parking during the summer air conditioning, a sharp increase in engine temperature and boil. In urban driving water temperature is high, but when driving on public roads, even if the air conditioning, the water temperature is normal, not exceeding 95 ℃.
Check Analysis: red car is fully enclosed forced circulation cooling system, in normal operation, the system pressure of 120 ~ 150 kPa. Special cooling fluid can not boil at 125 ℃, during normal engine operation and coolant temperature up to 105 ℃. Water to maintain normal engine by the thermostat, radiator and cooling fan. The cooling system of the engine to the radiator heat is transferred by the auxiliary cooling fan. The cooling fan has three gears (FIG. 1). First speed running condition is an air conditioner is turned on, then the X-ray 12 V voltage via the external temperature switch rarr; C switch rarr; diode rarr; 1 speed fan relay rarr; ground. Fan speed relay is 1, a cooling fan at a low speed gear. There is a work light switch on the air conditioner, when the air conditioner is turned on, this lights. 2 is a block operating conditions the coolant temperature of 95 deg.] C, the contact time in the low temperature double switch is closed, the second speed fan relay operates, the cooling fan speed to medium speed 2 operation. 3 is a block operating conditions the coolant temperature reaches 105 ℃ or air conditioning of the line pressure reaches 1 600 kPa. The temperature reached 105 deg.] C, the temperature of the high temperature inside the two contact switch is closed, the fan speed relay 3 is turned on, the cooling fan at high speed to third speed. When the air conditioning system of the line pressure of 1 600 kPa, air conditioning high pressure switch is closed, the fan speed relay 3 is turned on, the cooling fan at high speed to third speed.
FIG 1
by the above analysis, taking into account the vehicle running on the road normal temperature, normal cycle cooling system is the initial determination , but heat is not good. So first clean the radiator and check the radiator fan. Start the engine, the open air, the air conditioner switch indicator light radiator fan starts low speed operation, cooling fans and fan described relay block 1 normal; indication when the engine water temperature to 90 deg.] C, the cooling fan speed operation, low temperature switch described bis contacts and fanRelay 2 normally block; indicating when the engine water temperature continues to rise above 105 ℃, the radiator fan speed does not further increase. Suspected failure may be a double or a temperature switch fan speed relay 3 damage. Dual temperature switch disconnect plugs with wires connected across the hot junctions, cooling fan at a high speed, indicating good fan speed relay 3, a dual temperature judged switch is damaged.
Solution: Replace the dual temperature switch, radiator fan speed operation returned to normal, the open air temperature is not too high the engine.
reviewed: That embodiment is a two-temperature switch failure induced damage to the high temperature end. In general highway in the open air temperature is normal, because the large amount of wind when the vehicle is traveling at high speed, has played a role in cooling fan. Parking and low speed small amount of wind, the fault will be shown.
(FAN memory element)