Hello all. I have a 99 Lexus RX300 with 175k miles. A couple months ago, I woke up to dead battery and was told to replace the battery and subsequently the alternator (since the alternator read as undercharging). However, it turned out that didn't fix the issue as the car would still be dead on me only a few days later again. (I try to drive the car 3 times a week for at least 30 minutes, highway speed)
So, I had another mechanic inspect and they told me there was a draw coming from the back dome light (they disconnected) and the whole instrument cluster was replaced because my battery idiot light didn't come on when starting the car (It was explained to me that having the light come on does a "pre-test" on the vehicle prior to starting to ensure the computer can effectively communicate with the alternator to make sure it is generating correct voltage.) So I probably didn't even need a new alternator. 🙄
Anywho, got all those things fixed and taken care of and had battery swapped out again for 3rd time. Car was able to start up perfectly for last 3 weeks once everything was resolved. Now, all of a sudden, battery was dead again on me this week after driving it only 2 days prior. Like I said: I try to drive the car 3 times a week for at least 30 minutes highway speed.
I had a 3rd mechanic take a look at the car today and he insists that I either left dome light on or door ajar...but that is impossible! Since I have had so many issues with this car, I make sure everything is off and closed properly. I explained to him that the only thing I did different last time I drove the car was use the sunroof and pour in bottle of fuel system cleaner prior to filling up. He did a voltage test on the battery, alternator, etc. and everything was working perfectly. And he tested there was no draw from the battery when car was off. He hooked car up on a jumper and had it idle for a few minutes, then turned off, re-started a few more times and said I was good to go and it was probably just a "fluke".
If there is no parasitic draw, correct voltage being supplied to battery, and the battery is only 3 weeks old, what other explanation is there as to why the battery died all of a sudden? I'm beginning to think there is another drain on the battery somewhere that is only intermittent? Any suggestions?
Only significant do that is a charging system that is not charging or a parasitic drop some parasitic draws have to sit in a garage for three or four days with a meter on them which has a memory which can then be analyzed to see if over time there were any draws. This does require a very good mechanic who knows what they are doing because of course every time you open and close the door you're going to get a draw so you might just disconnect the battery after it sits for a while if you don't want to spend that kind of money with the mechanic who really knows what he's doing
Thank you Scotty. I agree it's not worth the time and energy to have the intermittent issue addressed. Especially since another one can pop up at any moment in my experience. Instead of disconnecting the battery each time I park the car, would it be feasible to keep a jump start pack with the car and jump it if it's dead or would that decrease the longevity of the battery?
The alternator should recharge the battery with around 13.4-14.5 volts if it’s lower than that it no charging as efficiently and it needs to be fixed as simply as changing the voltage regulator/ brush assembly or replacing it whole, you test that after making sure the battery is 100% dead by testing the voltage and CCA “cold cranking amps” of it.
you have to check of there is a leak and you said there is no leaks so if you are sure about that then check the battery CCA the car cranking up is not on the voltage alone, if the battery voltage is giving okay and the CCA is below 70% or less and its a new battery change it since it must be under warranty, its the CCA you have to check and how you do that you hook the battery tester and go to the CcA test function and enter the same amount written on the battery and start the test, and test the battery internal resistance if its too high that means if the battery reads 12V once you try to start the engine it drops to 6V or even 0V and that wont crank an engine, the car battery internal resistance is 0.001 ohms
Body control module is failing. It controls the checklist shutdown procedure for all the on-board modules.
They are expensive. They can be repaired by a company that specializes in that. Google it.
An alternative is to install a manual battery disconnect switch at the negative battery terminal. Disconnect when you park for the day and reconnect when you're ready to use the vehicle again.
