Lexus RX350

Car Doctor Q&A: Did Changing My Battery Kill My Power Windows?

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In Latin, it’s called post hoc ergo propter hoc: a faulty assumption that because there is a correlation between two variables that one caused the other. Is our Lexus owner’s problem caused by swapping the battery, or are the two items completely unrelated?

Q.I replaced the battery in my 2009 Lexus RX 350 and I thought everything was fine until I tried to put one of the rear windows down. The driver’s side works fine, but the other three windows and the sunroof are all not opening. Did I short something out when I changed the battery and how much will it cost to fix it?

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A.Essentially the vehicle computer lost part of its memory when the battery was replaced. This is most likely a simple and free fix; the windows need to be re-initialized.

With the car running, go to each door switch and run the windows half way down and the all the way up. When you are doing this don’t push the switch so that the window automatically lowers all the way down.

For the sunroof, hold the switch all the way forward and let it run through a whole cycle while you push it forward. Here’s a video showing the process on an RX330. It should be the same on your vehicle.

You are not the first person to have this happen. Most good technicians when replacing a battery will keep the electrical system active through a verity of methods. Some will use a special adapter to the OBD (under-dash computer connector) port, other will run power from a portable jump-pack to the back of the alternator or fuse box.

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Personally, I prefer to connect a couple of small electrical leads directly to the battery cables themselves. The procedure is simple: I use a Li-Ion jump-pack and connect the leads to the battery cables. Then carefully remove the negative cable and then the positive cable. You need to be aware that the power is now being supported with the jump-pack so you need to keep the positive cable away from any metal to prevent a short or sparks.

Remove the old battery, install the new battery and connect the cables and remove your jumper wires. The vehicles computer memory stays intact and everything will work as it did before. This is also handy if your car has an anti-theft radio and you have lost the code.

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John Paul

John Paul