Car is completely dead until battery disconnect/reconnect - then fine

Asked by Jun 04, 2016 at 06:59 PM about the 2003 Lexus RX 300 Base AWD

Question type: Maintenance & Repair

2003 RX300, with 110,000 miles or so. We've owned for a few years, since
90k or so. No issues, other than battery dying if we let it sit for several days
without driving it. We bought a battery quick disconnect that mounts right on
the battery terminal to fight the passive drain issue, and that has worked fine
for last 2-3 years or so.

Recently we saw the VSC/Check Engine light come on intermittently. Since
we disconnect the battery and leave it that way until next time we drive car,
that seems to have lessened.

But now a new issue has emerged: if we leave the car sit overnight without
disconnecting the battery, the next day the entire electrical system is down.
No remote locks, no interior lights after manually unlocking/opening the door,
no dash lights with the key in the ignition, and no starting.

Oddly, this is "fixed" by simply opening the hood ('bonnet'), disconnecting the
battery with the quick disconnect, and then reconnecting it. Lights come on,
ignition key warning bell sounds, car starts right up.

So why would cycling the battery connection 'fix' this issue? What would
someone do if they didn't have the quick disconnect? Who'd a thunk that
would work? It appears like a completely dead battery, but that's actually not
the case.

I'm reluctant to take it to a dealer - sounds like lots of bad experiences getting
charged to replace all sorts of stuff that may or may not address the issue.

Thanks for any ideas.

2 Answers

237,515

Ok, let me get this straight, your original issue was a circuit was faulty putting a drain on the electrical system, aka battery and now something else associated to that same issue has surfaced. You have had a workaround for years and want it fixed properly? You don't have to take it to the dealer and pay his prices. You can find a local reputable mechanic to diagnose the issue and make the repair. Look at this video. This is what they will do. Finding electrical issues take time and time is labor cost....https://www.youtube.com/watch?v=KF1gijj03_0

2 of 2 people found this helpful.

Thank you for your reply. I am not clear at all that there was anything "faulty" initially, other than a poor 2003 design. From what I've read, these vehicles (and many other makes/models from that era, including a German one in my garage), were packed with electronic systems that inflicted a heavy parasitic load on the battery when the vehicle is switched off. For vehicles that are driven daily, or at least a few times a week, this isn't an issue. But for vehicles like ours, that may sit idle in the driveway for a week or even two weeks between being driven, the parasitic draw is enough to drain the battery. The security system and remote lock systems are probably the sources - I've read other threads where people asked about disabling them in order to mitigate the issue. Modern electronics are designed to have much lower parasitic draw on a parked vehicle, so the drained battery issue is much less of a problem in newer cars. But back in the early 2000s, I think these systems were not as efficient, and so many cars from that era suffer from a similar problem. In any case, I don't think I had an electrical fault up until recently - no warning lights, etc.

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