Strange Mitsubishi Pajero V73 multi-information display unit no fault

an annual output of 2003 Mitsubishi Pajero V73 sport utility vehicle, with mileage of 170,000 km, the user repair multi-function information display unit (Figure 1) can not display information.


Pajero V73 is imported models, based on past experience in the maintenance, the electronic control unit rarely fails. By asking the user to know the car and therefore the fault has been overhauled in other pits, but the problem can not be resolved, specifically how to overhaul unclear.

In this car, multi-information display unit to display information primarily outdoor temperature, altitude, atmospheric pressure, time and date, a compass and a number set by the user, the user can use the displayed information to understand where the vehicle the location of data, you can set maintenance tips, you can also set the language and display units. The fault symptom car, I suspect the power supply problem of the display unit, it is decided to check the power supply of the display unit. So I first remove the display unit, wiring is then inserted rear measured normal power supply. Measured after removing it found that there is a red wire supply, a ground line normal measurement. In order to determine the exact point of failure, the author reviewed relevant circuit diagram of Pajero V73. A circuit diagram (FIG. 2) seen from the, multi-information display unit there are three power supply terminals, respectively, 24, 25 and 26 feet. Found by measuring only 26 feet has power, check the No. 4 and No. 8 has been burning fuse. After replacing the fuse, test found the multi-information display unit back to normal, but it was not long before the display unit can not show. Again check the fuse, the fuse 4 Discovery burning by 15 A, may be determined where there is a short circuit.

FIG. 2

After checking that the circuit diagram, a fuse 4 for the ignition switch to stop the display unit in the cigarette lighter, and the multi-information ACC power lines provide protection. When prompted circuit diagram, I carefully examined the No. 4 line fuse to the multi-information display unit number between 25 feet and found no short circuit, also did not find the presence of wire breakage phenomenon. Then remove the cigarette lighter, measuring 4 to fuse the cigarette lighter power at the center of the seat, and no sign of short circuit and wire breakage.

service point, I feel a bit puzzled. There are no line short circuit, grounding place, but why is it always burning fuse No. 4? Measured from the time of the fuse to a circuit at the electrical conduction indeed, and the measurement is completed and then measuring whether the fuse of the grounding, the measurement results are normal. Is multi-information display unit has an internal short circuit in place? After re-connected information display unit measurement or normal. In order to determine whether the problem is inside the multi-information unit, it replaced the multi-information display unit. Test again, the display unit displays information normally. It seems the problem is inside the display unit, then replace the multi-information display unit. After the replacement, the test failure did not occur again, then the car delivered to the user.

However, before long, the car for the same fault Depot again. At the fuse with a multimeter measurement, the found where there is a short circuit. But in order to check Shique open all connectors are normal, and then from the measuring circuit at the fuse is not a problem, is it I overlooked something? Then asks the user what operation is carried out after maintenance, adjustment only said user information displayed on the user setting information unit, with the cigarette smoke through the primary point. User heard mention cigarette lighter, I suddenly thought, cigarette lighter in the measurement line is removed, and the event of a fault cigarette lighter cigarette lighter is installed in the seat, is it caused damage to the cigarette lighter short circuit? It was found by measuring, when the short circuit cigarette lighter plug, when removing the normal line. View cigarette lighter were normal, remove the cigarette lighter seat checked and found cigarette lighter seat card with a piece of metal. Just short to ground by a cigarette lighter plug in metal block, resulting in the 4th burning fuse. The reason why I found no problems when checking line, because the cigarette lighter is removed.

After removal and replacement of the fuse metal block, test troubleshooting.

Summary: Review of the failure of the repair process, Maintenance ideas is no problem, but consider not comprehensive enough, omits some details in the repair process. I used to listen to others say ldquo; success depends on details rdquo ;, this truly understand the true meaning of this sentence.

(Chenghuai Yu)

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