bradykp

Hello - my father's car is around 180,000 miles. battery was going dead, so we put a brand new battery in. Alternator was tested and is working. When you start it and let it idle, it doesn't "high idle", it idles at around 500 RPM, and then if you turn anything on (lights, air, heat) within 5 minutes, the battery shows as dying with a meter attached to it. if it discharges below 12v for a certain amount of time, the car will just shut off.

one mechanic thinks it needs a new computer, and that only the dealer can install that?

another guy thinks it's a "regulator" that is between the computer and the alternator, because sometimes they go bad.

anyone have any experience like this? what's our best course of action? 180k doesn't seem like a lot of miles....

Hayk

iTrader: (1)

I'm guessing that the low idle is what's causing the battery to die. The engine never reaches enough RPMs to turn on the alternator, so the battery doesn't get to recharge. If your car was older, I would have recommended checking your Idle Air control, but I think that's out of the question.

bradykp

so any ideas on what might cause a low idle?

brucelee1

iTrader: (2)

I would take it to Lexus. The good news there is that if the fix they do doesn't, they won't charge you for it.

I did that back a ways. Lexus said it was the ECU, and it was not. They left in the ECU and ate the cost.

hypervish

Did it idle low before the battery change?

The ES will relearn the idle once the battery is disconnected, have you tried driving it around?

Are you sure there is no parasitic load?