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Tom, ASE Certified Technician
Category: Lexus
Satisfied Customers: 25954
Experience:  ASE Certified Master Technician qualified to work on all makes and models.
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99 Lexus ES300: battery ran..ran down..idling..headlights on and heat

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'99 Lexus ES300 battery ran down while idling for 1.5 hr with headlights on and heat on. It was 50F outside, I set the heat to 73. Did not realize my headlights were on (auto). Engine was running, idling around the usual 750 rpm. After 1.5 hours of this, the battery light started slowly getting brighter. I pushed the accelerator a bit and the battery light disappeared. I typically run down the battery several times a year. Trusted mechanic fully charged it a week ago. Mechanic tested the system multiple times. Tested leakage currents with the car off, tested alternator/battery probably multiple times. Mechanic already replaced battery, alternator, clip that connects negative terminal to the cable. Should a battery be getting drained while idling with headlights and heat on like that? I used to think it's because my daily commute is 5 miles one way and I usually have loud stereo, full HVAC, GPS, sometimes charge a phone, sometimes radar this normal? I don't think I had this kind of problem with any previous cars.
Have all fuses been checked in the under hood fuse box?Also has a parasitic draw test been done?
Customer: replied 6 years ago.
They did the parasitic draw. I'm not sure if they checked all the fuses. I looked at them myself, and at least the clear ones where you can see the conductor looked OK.
Were the actual fuseable links checked ?Also whats the alternator charging under extreme loads?
Customer: replied 6 years ago.
I examined fuseable links visually, did not test with ohmmeter. Autozone tested battery when I bought the car, found defective, replaced 6/21/2008. Shortly after that changed oil, tires, coolant hoses, idle air control valve assembly, gasket, timing belt/pump/drive belts, tuneup. On 1/9/2009, battery light would light up while idling at stop lights. Took the car to mechanic. Said if the battery was bad he couldn't test the alternator until after the battery was replaced. Battery tested dead, replaced the same day. Alternator tested dead, replaced the next day. I had to charge the battery more times than I can count, summer or winter. 11/8/2009, took the car in for service again (electrical). Says the only thing wrong was the negative battery terminal (loose, I think); replaced the same. Whether anyone tested at high load I'm not sure. Hood latch is stuck closed, I will test the charging at full load as soon as I figure out how to open it.
Ok that's what needs to be checked next . If the cable broke at the latch it will need to be opened from under the car or by removing the bumper. If it came loose at the inside latch then you will need to pull the cable from inside.
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