Case 1
Failure phenomenon: a 2009 annual output of the new Chery Cowin car, equipped with SQR477 engine. According to users complained that after the installation of a car alarm, then find air conditioning does not work.
Figure 1
check analysis: because the air conditioning was not working after the installation of anti-theft devices, so the focus should be checked on the line, particularly a line requires disassembly and modifications when alarm installation. First verification failure phenomenon, conditioned press A / C switch work light is on, the fuse is not blown, with reference to a circuit diagram of the air conditioning system (FIG. 1), measured using test lamp No. 2 low voltage supply terminal 12 V No, to No. 2 terminal of the low voltage load 12 V power supply, air conditioning system is operating properly, indicating that the fault point is not after the low pressure switch, also ruled out the problems related hardware (including low voltage switch, the air conditioner control unit, a compressor and an electromagnetic clutch high after the low-voltage switching circuit), a fault point described in the a / C switch to the line between the low pressure switch.
FIG. 2
Since Chery Cowin use a fixed displacement compressor, in the vicinity of the evaporation tank cockpit evaporator 1 after the temperature switch open A / C switch, 12 V power supply through the first evaporator temperature reaches the low voltage switch. At this time, measured by the evaporator temperature test lamp switch terminal number 1, no 12 V power after opening the A / C switch, thus locking the fault point A / C switch to switch between the temperature of the evaporation tank, further narrow the range of fault. A measurement with a multimeter / C switch to the line between the evaporator temperature switch, both not found turned right circuit breaker is it? Remove member associated with a wire harness and is found open or interference point. Can be seen from the circuit diagram, opened after the A / C switch, A / C switch output 12 V power to the air conditioner relay terminal No. 2, measured using test lamp relay terminal 2 normally receives 12 V power supply, but opens A / C I did not hear the air conditioning relay (FIG. 2) pull the switch. Conditioning test lamp measured relays the pins, the pins of the relay found no power (except A / C switch output 12 V power to the air conditioner relay terminal No. 2). C relayAfter the power source is a pull by the blower relay, the power supply to the air conditioner relay output terminals 8, measured with a multimeter block off continuity between the two, and found that both non-conducting. When the 12 V power supply through B / 4 terminals and TQ3 / 10 from blower relay output terminals, if B / 4 terminals is faulty, the low voltage to No. 2 terminal of load 12 V power conditioning system can not be seen from the circuit diagram work, so no need to consider the possibility of failure of B / 4. Then check TQ3 / 10 terminal, connector found TQ3 (FIG. 3) at the rear of the central relay box, found TQ3 / 10 terminal off, because the tight bundling tape caused when the wire harness installation of alarm.
Figure 3
Troubleshooting: resumes normal operation TQ3 / 10 terminal fixation, the air conditioning system.
reviewed: air conditioning does not work is the failure occurs after the installation of anti-theft devices, so too should focus on examination of disassembly during installation of security harness. The root cause of failure car, when the tape is used to install the wire harness bundling alarm caused due to too TQ3 / 10 terminals out.
Case 2
Failure phenomenon: a 2009 annual Chery Tiggo SUV, equipped with ACTECO SQR481 engine, mileage 1 200 km. According to users to reflect, occasionally fails starter does not work when the car is started, while the failure of the electric window regulator and central locking are unable to work.
Check Analysis: after communicating with the user that, simply by disconnecting the battery positive terminal, and then installed it can properly started. Fault user station does not occur the starter does not work, the author analyzes comprising the possible causes of the phenomenon described user: Ground line virtual connection or poor contact, a virtual connection exists phenomenon connector, a power supply line is bad. Since the fault is intermittent, so I decided to take exclusion investigation, first check the positive and negative battery terminal post, and found no doubt, related to the control unit on the body and the grounding line connector fastened, no Ground virtual connection and virtual access connectorThe phenomenon. At this time, start the engine, the starter does not work fault occurs, found lifter, central locking, lighting systems and other electrical appliances do not work when the authentication failure. See starter circuit diagram of a power supply, it found that the above electrical power with 60A fuse is provided by a positive line of the fuse box B /, then remove the positive line of the fuse box, see B / 60A fuse (FIG. 4) fixing nut from loosening.
Figure 4
Troubleshooting: fixing a fastening nut, failure to completely eliminate test.
reviewed: Since the positive line of the fuse box B / 60A virtual connection, the starter relay 30, causing electric uncertain, leading to the starter does not work. Due to the positive line of the fuse box B / 60A control unit E also provides constant power supply terminal to the vehicle body, so when a failure lifter, central locking system and corresponding lighting appliances not work. As for the user as long as the failure of said battery positive terminal reloaded once the fault disappears, because the user to reinstall the battery positive when the drag wire harness such that B / 60A came in contact with the fuse, so the fault disappears a.
(Semin wide)