Failure Case 1
Failure phenomenon: a 2006 model year Ford Mondeo sedan, mileage 56000 km. The car due to battery power loss, resulting in the engine not starting properly.
inspection and analysis: The author, after communication with the owner that the car parked in the case confirmed the lights off at night, the next morning a vehicle will not start properly. After initial diagnosis, the author identified as battery power loss, then the relevant system for further examination.
1. The detection of battery and generator
(1) start the vehicle, under appliances fully opened, the charging voltage is first measured with a multimeter generator is about 13.6 V, a normal within range, followed by a discharge current detecting a vehicle multimeter is 0.18 a, and no abnormality.
(2) to charge the battery after nearly 4 h, battery tester detects the battery discharge, the results show a normal pointer biased towards the green region. Then again with Ford WDS special fault diagnostic for detecting the output waveform of the generator and frequency generator during idling is read frequency of about 1 000 Hz, to determine the generator is working properly.
normal batteries and generators can troubleshoot the battery and the generator, the author analyzes the car certainly exist elsewhere leakage.
2. Detection of specific parts of the drain
first check whether the car install other electrical equipment. The investigation found no installation of electrical equipment, followed by multimeter functions WDS vehicle leakage test case again, in good agreement with the measured data before. 0.2 A by the current of the supply current is not completely dormant module, if the test time is longer, the current should be smaller. So I continued the test nearly 8 min, during which found that the current reading will rise about 1 min intervals, then the recovery of about 0.16 A. This phenomenon shows that, in the case of a vehicle ignition switch is turned off is still used in intermittent electrical work. So I disconnect fuse all the usual electrical appliances, above disappears, then plug it back in one by one fuse when the fuse is inserted to No. F66, the above phenomenon occurs again. Number of confirmed fuse F66 supply power seat fuse. The author of the power seat is adjusted, the seat height adjustment foundWhen no response of the seat, and the seat position is always at the top end, but always in the ON state of the switch further.
At this time, finally identified fault cause, because the motors are electric seat adjustment control module, which constantly switching between the working state and the protection state, thereby causing the battery discharge gap, so I concluded that this failure due to failure of a seat adjusting switch.
Solution: Replace the seat adjustment switch, troubleshooting.
Failure Case 2
Failure phenomenon: a 2006 model year Ford Mondeo sedan, mileage 76000 km, leaving for a week after users complained that the car can not be started.
Check Analysis: First, the battery charge maintenance personnel 3 h, the attempt to start the vehicle is fully charged, smooth start of the vehicle. At this time, a check of the charging voltage of the generator with a multimeter, the idle charging voltage 13.5 V, normally. The headlamp blowers and other electrical equipment and opened to increase the load of the generator, the charging voltage drops to 12.4 V. Increasing the engine speed to 1 500 r / min, the generator output voltage reaches 13 V. At this time, then entering the WDS Ford special diagnostic viewing PCM data stream generator, not abnormal, normal charging point based generator.
multimeter current discharge current vehicle speed is detected. Remove the negative battery cable, connecting the negative battery with a multimeter and body grounding line, lock of the vehicle, the current value falls within. 200 mA 10 s. Since generic electronic control unit GEM with a delay of a waiting time of about 20 min, this period of time will remain substantially constant 200 mA. After 20 min, the current value dropped to 50 mA has been the same, indicating that the car elsewhere leakage phenomenon (normal value should be about 2 mA).
The author observed by pulling a fuse checking method multimeter leakage current value where, when the number pulling fuse F7 current drops to 2 mA. FIG check circuit that, powered by a fuse with a number F7 F68, F60, F65, F66, F70, F71, F72, F73, F74 and the battery power relays. Unplug one by one the above fuses and relays, power relays disconnect when the current value drops to normal. due toPower relay control by the GEM, the author tries to replace the GEM, the failure remains. Windows and doors are controlled by the GEM, the fault will not be a problem because the doors and windows caused it? So I circuit inspection doors, no abnormal. Now the circuit diagram again, the author of the relevant circuits of all fuses by F7 (50 A) were analyzed power fuse, a fuse found F61, F62 of power windows, door powering lamp F99. In other words, the F61, F62 after unplugging, you can determine the door of the circuit there is no problem. When you disconnect the fuse F61, the F62, the fault remains, which confirmed that no abnormal door circuit, then the battery is almost certain there is a short circuit of the power control relay. After careful examination, we found the line there is wear and tear, causing a short circuit.
Troubleshooting: After repair worn line processing, fault disappears.
reviewed: When the battery power loss in service failures, we must first confirm whether human-induced. Such as: if the owner forgets to close all kinds of lighting, without the installation of electrical equipment. Then drain storage battery charge, the vehicle body for each inspection system. Check the battery should be observed peep holes is green state, then the operating frequency of the oscilloscope waveform and detecting the generator. This can correctly judge whether the normal charge situation.
When the system leakage test body, the method can not be negative battery body ground line and in series with a small bulb, this does not reflect the true situation of leakage. Discharge current must be read with a current detection function battery tester, the current value of the normal range if the test, the test for extension of time to respond, in order to correctly determine the failure, to further improve the quality of service.
(Li Zhaozhen)