Six weeks ago, a customer brought us their 2013 Porsche Cayenne. We have been working on this car since 2017. So far, all the work has been normal maintenance. The customer states a message in the center displays that the battery is discharged more than 50% if no one drives the car for three or four days. For the past six weeks, we have been chasing an intermittent battery draw. The customer states that the problem had started in the past month before bringing us the car.
We first checked the charging system and battery. The alternator charges 14.5 volts and 80 amps at 2000 RPM (alternator OK). The battery was replaced in September 2023 with a factory Porsche battery, yet we still tested it. The battery tested at 10.6 volts at 300 amps (battery OK). Even though we knew the battery was OK, we still charged it due to the fact it was being discharged.
We then tested for a parasitic draw (electrical drain). In the first few hours, we could not test a draw. After about five hours, we could see that the car had an intermittent 1 amp draw for about four minutes. The acceptable draw for this car is .050 mil amps. We then tested the car for the next 48 hours. Every four to five hours, the car had an intermittent draw between .6 and 1 amp for approximately four minutes.
We then asked the customer if anything had changed with the car in the past few months. The customer stated that they had an aftermarket dash camera installed, an aftermarket backup camera installed and an aftermarket kit installed into the entertainment system to use the CarPlay app. We then found out the entertainment system (radio head) had to be removed to install the CarPlay kit. The kit came with an updated electrical board and wire harness. There was a good chance that one of these aftermarket systems was causing our problem.
We must remember that we cannot see the draw until the car goes to sleep and sits for four to five hours. If lucky, we could see the draw twice a day, but usually only once. The first thing we did was disconnect the dash cam and start testing. We had to test for three days to confirm that the draw was still there. Next, we removed the radio head, and the backup camera was disconnected. We got the same results for the backup camera as the dash cam. The draw was still there. We then disconnected the radio head and tested it for several days. The draw was gone.
We then disassembled the radio head and found some interesting things inside. The aftermarket electrical board came with a ribbon-style wire harness. We found that the installers of the board did not route the wire harness very well. We also found that the Global Positioning System (GPS) antenna cable was damaged in the insulation. We then properly routed the ribbon harness and put insulation on the GPS antenna cable. We then reconnected the radio head and tested for a draw. Luckily, no more draws. We made sure to test the car for one week before ordering parts.
We had to wait a long time to get a new wire harness and GPS antenna cable from the aftermarket manufacturer. The primary reason this repair took so long is that the components were aftermarket and the duration of test time (waiting for the car to go show the draw). I always recommend that people not have aftermarket equipment installed into your car. If you really want to have a specific feature, look for a car that has it from the factory already.
Matt Pataky owns Sunnyvale Foreign Car Service, 15 Pioneer Way, Mountain View. For more information on his buisness, call (650) 960- 6988, email [email protected] or visit sunnyvaleforeigncar.com to learn more.
