Failure phenomenon: a 2009 annual Shanghai Volkswagen POLO 1.6 L sedan, mileage 31000 km. Car users reflect the right and right rear parking lights M3 M2 (i.e., right front, right rear small lights) is not lit.
Analysis Check: After I pick, first test, open light switch E1, and a right rear and right parking lamp is not lit, the user confirms the phenomenon described. The author preliminary analysis, may cause malfunction of the car include: light switch, faulty fuses, light bulbs and related lines. The right and right rear parking lights are not bright, the lamp is unlikely damaged, like a fuse blown due. Powering the right and right rear stop lamp circuit fuse SB12 (5 A) located on the instrument panel on the left side of the fuse holder, so I remove the instrument panel on the left side relay fuse box cover, SB12 examination revealed the fuse has been blown. Thus When the new test fuses, fault disappears, the right and right rear stop lamp capable of normal lighting. I continue to test for some time, the fault does not reappear, then delivery of the vehicle to the user.
After one week, the car again for the same fault to the site for maintenance. I first check and replace the fuse before SB12, I found and blown up. This shows that the fuse is blown not due to accidental high current line caused the line there should be shorted to ground and, therefore, can not easily replace the fuse, you need to carefully check the relevant line.
FIG 1
The author was careful analysis circuit diagram (FIG. 1), the right to know the car parking lamp current profile and right rear line: from the battery often the positive terminal of the power source 30, delivered through the red wire to T17 / 15 terminal E1 of the light switch, when the light switch is turned on E1, a current from T17 / outflow terminal 14, and connected by a gray / red lead and internal E108 fuse reaches SB12, and two branch lines are formed: a direct line to a right rear M2, then line 86 is grounded via a ground connection; T11a another line 11 via a pin plug socket compact composition D of 8-bit terminals (T11a / 8) reaches the right stop lamps M3, and finally through the ground line 85 is connected to ground.
analyzes clearly the right and right rear stop lamp circuit, short-circuit point I investigation will be more clear thinking.First, remove the fuse SB12, the resistance between the fuse insertion opening 12b and the ground measured with a multimeter, resistance was measured as 0.6 Omega ;, existence of a short circuit between the described fuse and ground. To further determine the short-circuit point, I take the measurement method checks segment. First, remove the right front headlight pin plug 10, measured at this time is still short between SB12 and the ground line described right front headlight plug after normal; 11-pin plug and unplug the compact T11a plug socket combination, and measured again SB12 resistance between the fuse insertion opening 12b and the ground is infinite measured result, the short circuit disappears.
After the above measurement, so that the failure was reduced further, substantially locked on the compact combination of 11-pin plug socket T11 / a between the right front headlight, which is referred to above current analysis short circuits, two branches of the second branch. 8 So I multimeter measurement terminal 11 of the pin plug T11a (T11a / 8) right front headlight No. 8 pin plug 10 between the terminal (T10b / 8) resistance, and hand shake associated wiring harness, the fluctuation near the ABS pump when a harness, found the multimeter readings constantly changing, carefully review found that the harness has been worn ABS pump mounting screws. The wire harness is a right parking lamp power line, and the damaged portion of the screw contacts shorted to ground, resulting in overheating of the fuse blown SB12. I carefully check found that plastic clamp to fix the harness off, resulting in harness with ABS pump mounting screws friction, eventually led to this failure.
Troubleshooting: repair and re-fixing the wire harness, failure to completely eliminate.
(Caoshou Jun)