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Q: Electrical short

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Put a new battery in my 89 Nissan pickup about six months ago. Everything has been fine. Last week I went to start it (I only drive it once a week) and the battery was dead. Charged the battery and it started. Let it sit for a day and the battery was dead again. Took the battery out and charged it. It is holding a charge while not in the vehicle. There's a short somewhere. Any ideas? Thanks, Vern

First measure the "total" parasitic load while the battery is connected (use ammeter or volt ohmmeter). Make a note of that. Ordinarily, you could have 20 to 50 milliamps or so of current draw to run the car alarm and security features. You’re looking for loads beyond that small normal current draw.

Using the main fuse box, systematically measure current draw circuit by circuit until you find the (hopefully) one circuit that has the excess current draw. Then you have to track down the component or wire on that circuit that is responsible for the excess current draw.

As a temporary measure, to solve the battery discharge issue while you are tracking down the wiring/component fault, you could always install a battery cut off switch on a battery post but when using such a switch you will lose your car alarm and might also cause stored info in PCM to be lost, necessitating a re-learn every time you run the car.

If you’re unable to pinpoint the issue, feel free to enlist one of our mobile technicians who can come to your home to diagnose your draining battery and help you fit it accordingly.

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