Another Dead Battery Mystery...

[Montalvo]

I have a 2000 RX300 and have had intermittent dead batteries over the last six months. Until recently, they've been separated by two to three months and I assumed that I had simply left a door ajar and the dome light ran the battery down. I switched the dome light off and stopped using the automatic headlights but still occasionally had a dead battery (always at home, fortunately). But when I called AAA three weeks ago for a jump, the guy tested my 18 month old Wal-Mart battery and said it was no good. I took it to Wal-Mart and they hooked it up to a large machine, waited ten minutes and then proclaimed the battery OK. Back home again and two days later…another dead battery. This time I insisted on a replacement under the warranty and Wal-Mart gave me a new battery. I brought the car home (after a 15 mile freeway drive), got into the car three days later and…dead battery!

I've read through the various stories on this forum describing similar complaints. But I checked the alternator prior to getting the new battery and was getting 13.5 volts and my battery is brand new. I pulled off the cables and checked for resistance with my ohmmeter (set at 1K ohms)…no resistance at all. So I began methodically removing all 53 fuses, testing the resistance between the battery cables after each fuse was removed. There was no change in the resistance (i.e., it remained at zero) with each of the fuses I removed. But I was unable to pull out two of the fuses (big ones): ABS (60A) and alternator (140A). Any suggestions on how to remove them? They're very hard to remove and I'm afraid I'm going to break them.

And I also removed something in the main fuse box under the hood that looked similar to a fuse but was labeled "SHORT, D.C.C." on the fuse map under the fuse cover. (I saw this mentioned in an earlier post entitled "Battery Drain Problem".) When I removed it and tested the cables for resistance, I got what looked like 4 ohms of resistance instead of zero as with all the other fuses. Does that mean anything? (Please don't tell me that by pulling that out I've trashed my ECU! :cries: )

Thanks for any suggestions you can offer.

Bob

[LexKid630]

I had a similar problem with my 2003 Rx300. One day the battery was just dead. Took it to the dealer, the battery was ok, and the alt. was ok; they later found that the driver's door lock was "catching" causing a drain somehow. They lubricated it and everything's been fine since.

Hope this might help?

[mehullica]

Why are you checking resistance? Current draw (amperage) is what should be check for a parasitic draw.

[Montalvo]

Why are you checking resistance? Current draw (amperage) is what should be check for a parasitic draw.

I guess I assumed that when the key wasn't in the ignition, there shouldn't be any closed circuits and the resistance should be zero. But now that I think of it, the car's anti-theft system would still be drawing current and perhaps other things that don't represent a "problem". If I check the current draw, what level of draw would tell me if I've got a short or malfunction. And would pulling fuses allow me to isolate what circuit was causing the problem?

Thanks,

Bob

[Karl K]

I also had some battery problems recently. It was the battery that needet replacing. When I tested for currant draw, putting the ampere meter in seies with the battery, there was a 5 milliamp draw, which I think is fine.

good luck, Karl

[Montalvo]

I dropped the car off at a Lexus dealer this morning. They found an amperage leak and had begun testing to locate it when it suddenly stopped. They're going to keep the car overnight and hope that the problem resurfaces. But this reinforces my suspicsion that the problem is intermittent, since I had five or six dead batteries over the course of about six months. Of course, the downside is that intermittent problems can be the most difficult to track down so it'll be interesting to see whether the dealer can make effective use of their database of RX300 electrical problems to sleuth out a solution without the symptoms being in evidence.

I'll keep you posted.

Bob

[lenore]

there is a natural amperage leak that is associated with the automatic door lock mechanism, It times out after some specified period. The other device could be the CD player cartidge control, but I doubt it. Good luck, hope you got a tech that understands the electronics in the Lexus.

[Montalvo]

OK, I just got the bad news from the Lexus dealer. The problem was with one of the on-board computers...$845. But the woman told me at least it wasn't the $2,500 one. Small consolation. I was preparing to trade this car in when the new models came out this fall. Looks like time wasn't on my side.

With today's cars and their electronic controls, there are increasingly fewer repairs that can be done by the owner. But there are also fewer repairs that are necessary so I'd be the last person to go back to the "good old days"...oil changes every 1,000 miles, tune-ups every 10K miles, etc.

Thanks to all those who tried to help me out.

Bob

[mikey00]

OK, I just got the bad news from the Lexus dealer. The problem was with one of the on-board computers...$845. But the woman told me at least it wasn't the $2,500 one. Small consolation. I was preparing to trade this car in when the new models came out this fall. Looks like time wasn't on my side.

With today's cars and their electronic controls, there are increasingly fewer repairs that can be done by the owner. But there are also fewer repairs that are necessary so I'd be the last person to go back to the "good old days"...oil changes every 1,000 miles, tune-ups every 10K miles, etc.

Thanks to all those who tried to help me out.

Bob

Be sure and post back if their "guess" fixes the problem.

[SKperformance]

What computer did they say it causeing the loss?

[Montalvo]

I picked up the car today and assume that it's all better. The part that was replaced was the "body control module", priced at $461.04 plus $318 labor.

[SKperformance]

The BCM which can be a problem with many cars as it controls many features and can cause leakage easily.

[Montalvo]

Dang...SKPerformance, where were you when I needed that assessment? Sounds like I might've been able to save $300 in labor costs by installing the BCM myself, assuming that I could verify that that was my problem. Well, maybe your post will provide a clue for the next victim of amperage leakage.

Bob