Aftermarket September 2022

SEPTEMBER 2022 AFTERMARKET 33 was present in several ECUs. This gave us a place to start testing. See Fig.1. Fault-finding mission With this information in hand, my multi meter was attached to the battery and 15.34 was the reading on the screen. In order to catch exactly what was going on, a scope was used. When the vehicle revved up, the following trace was captured. It spiked over 18 volts. Please refer to Fig.2. It is a well-documented fact that these alternators suffer with harness faults. With this in mind, the harness was visually inspected from underneath. It all looked good up to the plug by the battery box. These are smart charge, utilising four connections. The large one goes to battery positive, then the three in the plug are as follows: One is used for battery voltage sensing, the next sends the ECU command signal to the alternator charge level request, and the last one transmits the acknowledgement signal from the alternator back to the ECU. The command and the acknowledgement signals are square wave PWM so I prefer to test with a scope for more accuracy due to a multi meter just averaging the signal. With the scope back-probed in to all three of the black plug wires, I could see the command and acknowledgement signals, but no battery sensor voltage was present. The next step for testing was to check the fuse, which was intact and ok. This corrosion I then removed the air filter housing to gain access from the top. This would allow me to test at the plug between the harness to the alternator and the vehicle harness. Next, the fourth channel of the scope was back-probed into the top part of the plug on the battery voltage sensing wire. No voltage was found here either, so a wiggle test of the harness was employed which caused the scope trace to jump up to battery voltage. At this point I pulled on the red battery sensing wire just above the plug and the insulation parted. Here we found what we were looking for; Corrosion, the green crusties of death for wiring. Please refer to Fig.3. The other wires were pulled to see if their fate was the same, but the scope trace stayed steady for the command and acknowledgement, so they were fine; No attention necessary. Then, a repair was made by stripping the terminal out of the plug and replacing it with a new terminal with 15cm of new wire attached, of the correct gauge and colour. The harness was then opened up and the green wire disease was cut out. A new wire was soldered to the clean old one in the loom, then covered over with heat shrink tubing re- tape. The loom was then put back up, we joined the connector back together and we re-tested. Above: Fig 2 Left: Fig 1 This confirmed the fix, with the battery voltage now present at the alternator plug along with the command and acknowledgement signals when the vehicle lights were switched on. The command signal was seen to alter, and with the vehicle revved up the voltage never went above 15 volts. With the fault codes erased, a final road test was in order. This time there were no dash drop-outs or engine cut-outs. When re-scanned, the faults for the overvoltage were gone. Some of the other faults returned, but these were a job for another day. The initial fault, cutting out due to overvoltage, was fixed. Paperwork done and keys returned to the office, my job was complete. I can confirm that the customer has had the van back for over a month and it has been faultless. Right: Fig 3