Throughout the winter my wife’s Subaru Forester, kept having battery problems. One day it would start, a few days later it wouldn’t. I trickle charged it a number of times (a really fun task when the temperature outside is five degrees) to get it up and running again but it didn’t seem to help, a few days would pass and I’d have to go through the whole process again.
The battery was pretty new, I had just bought it last year, but I assumed it was just a defective battery so I pulled it out one morning and took it to Advance Auto Parts to get it charged and tested. They called back in the afternoon and told me it charged up just fine and that it was still in good shape. That’s not what I wanted to hear, the battery would have been the simplest solution.
Since all else had failed, my wife scheduled an appointment at the local Subaru dealership and we dropped the car off in the morning so they could see what was going on. She got a call from them a few hours later, saying that the battery looked good and the most probable cause of the failure was that she wasn’t driving it enough to keep the battery charged. Modern cars have lots of electronics that are running even when the car is off and they believed that between the drain from that and the cold weather, the battery was discharging rapidly which caused the problem. Unfortunately, they found an additional issue. Mice had eaten through a wire in the wire harness that connected to the knock sensor. Even though the car would still run, without the knock sensor, it would most likely fail emissions test during inspection and would not be allowed on the road. There was also the possibility that under the right conditions, the engine could be damaged.
Sadly, things were about to get worse. Even though the problem was caused by a single wire being chewed through, since it was part of the wire harness the whole harness would have to be replaced at the cost of somewhere over three thousand dollars. On top of that, the wire harness would have to be ordered from the manufacturer in Japan and could show up in a week, a year or never. My wife thanked them and told them she’d discuss it with me and get back to them.
She told me about it and being a guy, I offered to try to repair the wire myself even though I know nothing about cars and didn’t even know what a knock sensor looked like. I even went out and opened the hood hoping that I’d see something obvious that I could fix but between my lack of knowledge and the fact that it was still five degrees outside, I decided it probably was not our best option.
We talked about it a bit. The car was purchased in 2017 so was getting pretty old. Maybe it was time to trade it in. On the other hand she’d take a big hit on the trade in, because of the problem, and the car only had about 18K miles on it so outside of the wire harness problem it was still in good shape.
In the end, she decided to spend the money and get a new wiring harness. The dealership put the order in and luckily they were able to get a new one delivered in less then a month and were able to install it in a couple of days. We picked up the car yesterday morning and it’s running fine and with any luck will continue that way in the future.
I did some research, hoping to prevent the problem from happening again and found that mice supposedly hate the smell of peppermint. I purchased some peppermint spray on Amazon and will be spraying our engines periodically hoping to keep the mice away.
$3800 lesson learned.
