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Parasitic Drain On Battery


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I have a 2000 Lexus GS400 and a brand new battery from Lexus drains in a week. This happens with the car sitting in the driveway not being driven at all. I have not left any interior lights on, and my battery cables are on nice and tight. I have a friend who has a 1999 GS400 and Lexus with the same problem.. Lexus could not find the problem. He is disconnecting the cable at night. I am in dire need of assistance dudes.

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I have a 2000 Lexus GS400 and a brand new battery from Lexus drains in a week. This happens with the car sitting in the driveway not being driven at all. I have not left any interior lights on, and my battery cables are on nice and tight. I have a friend who has a 1999 GS400 and Lexus with the same problem.. Lexus could not find the problem. He is disconnecting the cable at night. I am in dire need of assistance dudes.

Welcome to the LOC :cheers:

As I posted on another post, you should check your charging system. You can do the regular/normal tests like, checking the tension on your S-belt, checking the terminal/ground connections on the batt/alt, load testing both, etc. You can also hook up an ammeter to your batt & start sequentially unplugging your fuses/relays until the flow stops. When it does, you will have found the drain.

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can you explain how to hook ammeter in series with battery? do i put pos lead on pos terminal, or put one lead on batt terminal and the other on pos cable?

Ammeters should always be connected in series.

1 disconnect, the neg cable to the batt

2 connect the neg lead from the meter to the neg terminal of batt

3 connect pos lead to the cable

4 set the appropriate scale and read the draw

5 draw should be between 20 - 75 ma

6 anything higher than 100 ma is parasitic

7 initial reading may be high while systems are coming back on line after connecting meter

8 you can check readings by opening a door - should immediately go higher but return to normal once closed

You can also check for a batt surface discharge which is a small current that runs between the terminals across the surface of the batt if the batt is dirty

1 set the meter to read voltage

2 with the batt connected, attach the neg meter lead to the batt's neg terminal

3 connect the pos lead to the surface of the batt

3 if the reading is higher than 0.5 volts, clean the top of batt.

also, how do i load test batt/alt?

To load test the alt, take it to a shop you trust. You need to read higher amps than your meter is capable of. Charge is minimal. They will do the batt as well.

Hope this helps you out. :cheers:

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