With the development of modern automotive electronic technology in the automotive air conditioning system, either manually controlled or automatically controlled air-conditioning compressor electromagnetic clutch cut engagement generally achieve computer control.
In the repair process auto diagnostic software of the air conditioning system, a considerable part of the failure to appear on a computer. While in the case of all sensor signals can be input into the computer normally, when the computer can not properly control the compressor electromagnetic clutch separation and bonding, the fault position occurs mostly in a switch from the role of the computer's internal transistor.
To repair a computer, the first to confirm that is certainly a computer failure, so as not to blind repair, causing unnecessary waste of time and cause circuit failure. Computer repair theoretical basis and scientific methods, not recklessly, repaired computer can promise warranty period.
Air conditioning repair most of the computer control part of the fault, in fact, is to replace the computer-related switching transistor. Following Honda Accord 2.2 sedan, for example, to explain the methods and steps of computer repair.
The first step auto scanner is to find the electromagnetic clutch control the connection end of the coil and the computer and the ground terminal of the computer, according to the circuit diagram best found with crayons terminal marked.
The second step is to use digital multimeter measurement-off block, from determining the air-conditioning control terminals, find a little inward along the computer printed circuit until you find a triode or triode row.
The third step auto code reader is to determine triode or triode rows of three pins, computers generally use an NPN transistor, here NPN type, for example. Previous step found in the printed circuit corresponding pin is the transistor collector, corresponding to a smaller next to the printing line is the base of the transistor. Of course, need to be further confirmed what the left one or the right one.
Confirmed as follows: Set the air conditioning operation panel operation in air conditioning and refrigeration state voltage using a multimeter block is connected to a foundation to be confirmed pole cord, turn on the A / C switch, which should show 5V off switch should show 0V. Use this method to test the wires repeatedly confirmed shall comply with the conditions of the base. Recognized emitter, generally if the transistor row which emits significantly more measured with a multimeter off at both ends of the row of the stopper one end connected to a ground terminal of the computer and the other end received is considered to be a grounding end of the row, it is possible to guide through the pin is the transistor emitter. If only auto diagnostic tool one transistor, through the thickness of the printed circuit can be easily identified.
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