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Phantom Battery Drain- Help!


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I have a 1999 RX300. About 4 months ago the battery started going dead after 48 hours on non-use. The battery was 3 years old and tested fine. I had it recharged and again...the car went dead. I had it replaced. Same thing.

Since then I have had three different mechanics test every electrical system. All fuses were fine and nothing showed up on the diagnostic meter. I changed the Body Control Module. Still no luck.

Some issues that occured around the same time the battery started dying were: My key fob would not work on the door lock system. My 6-disk CD player would not load one disk properly. My right-front ABS brake sensor went bad after the transmission was replaced last year. I have since had the ABS sensor replaced.

Please give me suggestions or insight. I am willing to try anything at this point.

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I had a similar issue last fall with my 2000 LS400 - battery would barely hold a charge overnight and the car would almost not start after sitting all day outside in fairly warm (50+ degree) temperatures.. The problem turned out to be caused by corrosion - mainly on the cable clamps that prevented them from making good contact with the battery terminal posts. I cleaned the battery terminal posts and cable clamps with a cheap battery/clamp cleaning tool from Autozone and also with baking soda/water and a tooth brush and until they were bright and shiney. I then tighened the cable clamps to the battery terminal posts VERY tightly. The positive cable clamps don't have as much contact area as the negative terminal clamps so I think it is especially important that the positive cable clamps be clean - don't know if the same odd clamp design was used on your RX.

The corrosion didn't look too bad so I'm surprised it was enough to cause the problem and that I've made it through winter with a battery I almost discarded when it was only about 9 months old. Of course your problem could be different.

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