a 2003 annual Chery Cowin 1.6 L sedan, equipped with an electronic control system using Delphi’s Tritec engine, matching QR520 type manual transmission, mileage to 103,000 km, users reflect the door open indicator light. Cause
According to the author of maintenance experience, usually caused indicator light on the instrument panel of a door opening comprising: a door contact switch associated vehicle door is damaged, often resulting in a signal to the instrument to ground feed; parallel on all door contact signal line where there is a short to ground; instrument damage. After checking the relevant circuit diagram shows that the car door contact switch 4 belongs to a parallel state. Using this parallel, as long as the door is opened 1, the meter will display the vehicle door in an open state. The car 4 then contact switch is connected to the parallel combination of meter and ceiling, door opening control instrument for indicating and ceiling lighting during ceiling DOOR gear.
FIG 1
I successively remove the four first door contact switches, instrumentation and ceiling, measured with a multimeter line, the line was found to still be short-circuit, indicating the presence of the short circuit line associated door contact switch. Since the gate signal is in parallel contact state, if the lines can be sequentially spaced apart, it is necessary to check for all harnesses disassemble involved, a large workload. Based on past experience maintenance, door contact switch signal circuit nodes (FIG. 1) at the left front side of the pedals A column, so I found the A-pillar side node. Turn off each signal line, when the dome light off control circuit, grounding line disappears. Further examination found that the ceiling in the middle of the wire harness through the A pillar of the dome destined, since previous maintenance personnel installing the A-pillar trim dome pressed into the wire harness decorative board hole in column A (FIG. 2), causing the control circuit and A dome column metal shorting interference.
FIG. 2
After processing of broken lines, test troubleshooting.
Summary: This failure has two areas that need attention, first, although the fault is not very complicated, but quickly ruled out a critical fault line is to find a node, and then to be able to effectively carry out the separation line, thus eliminating the need for dismantling harness larger workload multiplier effect achieved; so that the twoBarrier is one case of human error, here to remind colleagues again, when maintenance work must pay attention to operational details, do not fix a fault but planted a hidden danger.
(Qin Zhigang)