How can I diagnose a slow battery drain that appears to be caused by the fuse labelled as "short" in the underhood fuse box
I have a 2005 Toyota Highlander Limited 3.3 that has had an ongoing slow battery drain issue. If I don't drive it every day or so, and in cold weather for a long enough time every day, the battery gets drained. If I remove the fuse labelled as "short" on the underhood fuse box, it stops, but that fuse enables a lot of the interior accessories, like dash lights, AC memory, Radio, etc that I would rather not have to do without. I purchased the car about 6 months ago from family and knew about the problem. The battery was replaced, as well as the alternator a month or so prior to my purchase in an attempt to fix the issue.
Since you know what fuse it is, now you have to pinpoint which accessory is your issue. You have to do some probing with your multimeter to know which one it is. I assume you don't have the knowledge to do so, so have a local shop help you out. You can tell them what you told us to help them along.
Tom is right, you're half way there since you know what fuse it is. I's known as parasitic drain. Since the dash lights are out, your taillights may be also. Looking at pictures of a Highlander, it does not look like the taillights are on the rear hatch, but the license plate lights are. Have a look at where the wires go from rear hatch to chassis, from 10 years and hundreds of open/close, that MAYBE it.
If you do have a multi-meter, normally the anti-theft and clock will draw on battery, but only a miniscule amount. Put it on 12V and set on amps, and disconnect Neg-- battery cable. Put leads between Neg battery post and ground cable terminal, or just ground it anywhere on the chassis. Normal draw with engine off, key out, is 0.25 amps. Or ¼ of 1 amp@12Volts
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