Configuration 8V engine and manual transmission Citroen. As the hot weather, frequent use of air conditioning systems, and found that air conditioning cooling effect is getting worse, specifically the phenomenon as follows: Press the air conditioning and refrigeration switch (Electric No. 584), air conditioning compressor to operate properly at first, but with the extension of working hours, use Auto Diagnostic Tool testing data showed that the air conditioning compressor electromagnetic clutch is frequent absorption and separation, intermittent failure caused by air conditioning refrigeration function.
Air conditioning system circuit diagram, the air conditioning compressor electromagnetic clutch frequent closing and analyze the cause of the fault separation, according to the possibility of making maintenance plan, and then to repair work as follows:
1) Check the engine compartment fuse box (Electric No. 52) of the fuse F12, normal. In the case of opening and closing of the ignition switch, voltage with a multimeter block measuring the terminal voltage connector 113 BIIA results were obtained for the battery voltage and 0V, normal. In the case of opening and closing of the ignition switch, air conditioner switch assembly measuring terminal 7 NA1 voltage, battery voltage, respectively and 0V, normal.
2) Replace the air conditioning switch, the failure remains. Replace the air conditioning control box, the problem persists, that failure has nothing to do with these two parts.
3) In the case where the engine is not running and the operation of detecting the line pressure of the refrigerant, the refrigerant is obtained by the static pressure of 500kPa, the dynamic pressure of the refrigerant: a high pressure of 1300kPa, a low pressure of 140kPa. The above measurements were compared with standard values, in line with requirements. This ruled out due to the refrigerant pressure abnormalities lead to the air conditioning compressor electromagnetic clutch pull and separate frequent failure factor.
4) Check the coolant temperature control box (appliance No. 53) and the related wiring. External line there is no problem. Replacing the coolant temperature control box test, fault still exists. Continue to check the fuse box in the engine compartment fuse, no abnormality was found. Check the coolant temperature control box plug voltage terminal 15N4,15N15 in the ignition switch is turned on is the battery voltage, Launch X-431 PAD or Launch X431 GDS tool coolant temperature measurements show that the control box supply line is no problem, thus excluding the coolant temperature control box failure factor.
5) Check the coolant temperature sensor (electrical No. 910 for coolant temperature control box to provide coolant temperature signal) and the line, there is no obvious anomalies. Replace the sensor, the fault persists.
6) Check the evaporator temperature sensor (Electric No. 912) and the line of work, there is no appearance problem. Measure the resistance with a multimeter evaporator temperature sensor found resistance is too large. Replace the evaporator temperature sensor, test, fault completely disappeared, ending maintenance work.
The evaporator temperature sensor is a negative temperature coefficient thermistor, its resistance decreases with increasing temperature. When the resistance is too big a problem occurs evaporator temperature sensor, the signal voltage will become larger, air-conditioning control box will mistakenly believe that the evaporator temperature is less than 1 ℃. To prevent evaporator freeze, air conditioning control box off the air conditioning compressor electromagnetic clutch operating power. After a child, Autoboss V30 SPX or AUTOBOSS V30 Elite tool checks found that the evaporator temperature is higher than 3 ℃, began to turn on the air conditioning compressor electromagnetic clutch pull. Again and again, the results of the air conditioning compressor frequent start of the fault phenomenon. The evaporator temperature sensor is a vulnerable part, only after the damage can be replaced.