bfg23

Do alternators go bad on these cars if they have to work overtime to keep a battery charged?

My wife was driving our 430 last night, and all of the sudden, the battery light appeared and the car just stopped. I was at a venue and busy so my father went out and took a look. He said the battery is shot and the alternator is not charging it.

He hooked up a dry cell battery he has and the car started no worries, but, as soon as the battery was disconnected the car died again.

I am going to have a look at the car now as its stuck at our friends house 30mins drive away, but im looking for opinions on whether the alternators go bad on these cars, or whether its because the battery is so far gone it will not hold any charge at all.

This is irking me.

KING

iTrader: (1)

Yep, an alternator went on me once.

I don't think the even had direct causation on this fault, but this is what happened.

I was doing about 140 mph on a deserted road for about a straight 10 minutes, right before then end of the road, as you said, the battery light appeared, along with all the other lights including the engine light.

I stopped for a minute or so, then started the car again, it started and drive me home, which was about 10 more miles, then it would just not start.

Figured it was the alternator since it ate a whole new battery. So I put in a used alternator and got a new battery, and the car worked fine from that time till I sold her.


So yes, maybe not a common problem. But does certainly happen.

BradTank

Yes, if your battery is shot the alternator keeps working "overtime" to try and charge it and can burn itself out.

When you buy a new battery, a good practice is to trickle charge it before installing as often times it can be low and it really works the alternator. Very few people actually do this though.

If you feel your battery is on the way out, get a new one. I've known people that will wait until it leaves you stranded and need a jump start. It's not good for your alternator to try and keep a toasted battery going.

Lavrishevo

iTrader: (1)

The car is smart enough to let you know the battery is bad vs the alternator. Alternators are not common and can often last past 200k miles. I believe your alternator failing killed your battery.

With the ML sound system and the car on you can hold the option key down and click the parking lights on and off 3 times to display a test menu. It's mainly for the screen and buttons but it also shows if your are getting 12+ volts. Turn off vehicle to exit. 3 clicks - on off, on off, on off. Good way to easily monitor your alternator.

Bocatrip

You can easily get a multimeter for 7 bucks on line and see what your alternator is putting out as well as the condition of the battery. Yes, it is relatively uncommon for our alternators to fail as they are quite robust, but things do happen. I'm not sure I would go with a cheap aftermarket alternator but try and get the Denso although it is more expensive. Good luck.

Tom57

You have a faulty alternator. Once the engine is started, the battery is not the major source of electrical current for spark, electrical components & accessories, etc. If the alternator isn't working properly, the spark and other components suck the remaining life out of the battery, until it too, dies. Here is a link if you need to DIY replace the alternator. I strongly suggest that you replace with a Denso OEM alternator. Saving a few bucks on an after-market alternator isn't worth the risks, hassle and peace-of-mind.
https://www.clublexus.com/forums/ls4...001-ls430.html

Tom57

This on-board diagnostic works only on '04 - '06 model years.

bfg23

I put a multimeter on it while running and the alternator is completely shot. 11.8v at the battery.

Thanks for the replies guys, Ill be chasing a Denso unit up after this easter long weekend.

Lavrishevo

iTrader: (1)

Nice. Thanks for clarifying. I did not know that.

jackies

iTrader: (5)

That sounds interesting - what are parking lights and how do you click them?
Pardon my dumb question.

Tom57

It's the first click on the headlight switch, left side arm off steering column.