Case 1
Failure phenomenon: a 2008 annual Shanghai GM Buick LaCrosse 2.4 L sedan, mileage 21000 km. It says users, good times and bad regulation power driver’s seat of the car.
Check Analysis: power seat is a dashboard fuse box of an electric circuit breaker of the seat (25 A) power, when the electric current is too large, the thermal protection circuit breaker disconnect the power supply, when the temperature is lowered to restore power. Normal power measurement circuit breaker, then the seat may be adjusted properly. After people get on the seat, the seat will not be adjusted after a few minutes, this time touching breaker feeling hot, so suspect line in place of a short circuit, resulting in overheating protection circuit breaker to enter the state.
Remove the breaker, measuring the resistance between the seat end of the power line and the ground is infinite, the driver’s seat is pressed by hand, no change in resistance. When the seat hand percussion, resistance becomes 5 MOmega ;, moment when a person on the seat side to side, resistor 3 MOmega; vary between infinity, but it will not cause overheating protection circuit breaker. Do people not enough weight on the seat? Then find people to take a large weight, when he sloshing around in the seat, the seat end of the resistance between the power supply line and the ground sometimes becomes 3 Omega ;, indicating that the power line is shorted to ground. Then remove the seat inspection, found friction between the seat and the seat slide adjustment switch harness, the harness has been worn through the skin (FIG. 1), it seems this is the reason a short circuit occurs.
FIG 1
Solution: Replace the seat adjustment switch harness and properly fixed, seat adjustment function returned to normal.
reviewed: seat adjustment switch harness frame through a seat slide, the edge of the seat frame iron rough, when people sit harness worn Insulation frame after exposure, lead lines short circuit.
Case 2
Failure phenomenon: a 2008 annual Shanghai GM Buick LaCrosse 2.4 L sedan, mileage 43000 km. Say users, is the brake light does not shine.
Check Analysis: First, verification failure phenomenon, the brake pedal when the brake taillight light does not shine, and the high brakeLight normal. Check the normal brake light, brake light can hear the sound of the relay is left dashboard when the brake pedal. The left side of the dashboard trim panel removed, and the voltage measuring relays moldings side brake lamp control were normal, after removing the drive relay to the battery, the output side of the two wire resistance pin 40 MOmega ;, is open. Open relay housing, found inside the movable contact fatigue fracture has welding (FIG. 2).
FIG. 2
Solution: replace the brake lamp relay, when the brake pedal in the brake lamp can taillight normal lighting.
Figure 3
reviewed: LaCrosse BCM car stop lamp unit controlled by a vehicle body, the brake pedal when the brake light lights but taillights the brake light is off, the normal brake lights fuse. Third brake lights and the brake lamp relay is described also BCM normal output, so long as the output control check stop lamp relay it. Further, the left inner Jun dashboard trim the two relays (FIG. 3), a brake lamp relay blue, black after the fog lamp relay, which needs attention.
(bovine head loss)