Alternator Or Battery Or...?

[Taz]

I've recently purchased a 94 LS400 and, unfortunately, don't know the history on the alternator or battery (however, the battery appears to be the right specification and is about 24 months old).

I've encountered two problems starting the car since I've had it. Both times the problems seem to appear after the car has gone undriven for 48 hours or more. The first time, I got the rapid click o'death and naturally thought it was time to replace the battery. However, after I went to start it about an hour later, it kicked right on over.

I went ahead and cleaned the battery posts and cables anyway. Any other starts were no trouble at all. In fact, the next day my wife left the parking lights on for two hours(!), but the engine kicked right on over none the less.

The following day the car was scheduled to go to the dealer for its scheduled maintenance. In spite of them telling me that their checkup includes ALL systems, I asked them to pay particular attention to the charging system. When I picked the car up, Lexus assured me that the charging system checks out fine.

The car then sat for about 48 hours undriven. I get out to start it this morning and while I didn't get the click o'death, it did not want to start. Got a couple of belabored moans and groans from the engine before it finally, and reluctantly, kicked over. I drove it at lunch today and it started normally.

Sooooo....anyone want to take a shot as to what the problem could be? I thought about just replacing the battery to see if that would "cure" things, but if I've got to end up replacing the alternator, I might want to mind my pennies.

Any advice...including any info as to what it might cost to replace the alternator at dealer prices would be appreciated. (If it's as expensive at the dealer as I think it is, I might look for another alternative).

Thanks,

-Taz

[VMF]

it could be a shortage somewhere. might even be in the battery itself. your charging system is fine since the engine starts right up after you drive the car. let me tell you this. when you will not drive your car for 2 days disconnect the battery connectors. connect them right before you start the car. this will tell you if the problem is in the battery or in the car.

[SKperformance]

it might be a charging system problem with the alternator not always giving full power when shut off thus leaving the battery not at full charge

also might eb a problem witht eh wires for the batt and starter being corroded or the battery ground to the body

i changed my starter and body wires and the car works much better now

my alternator is still a problem with heat where it will not give a full 14 volts when it is hot and at idle

[VMF]

but he said after driving car starts right away. the problem shows up only when the car is not in use for long periods of time. i had a problem with charging system. my battery indicator went on while i was driving and all the lights were dimmed. the charging problem is easy to test. just connect volt meter to the battery connectors while engine is idling. it should show around 14V. if its much less (around 12) it means there is no charge and then the chargin system has gone bad. try to rev the engine and c if its going to increase the voltage. if not then trouble shoot ur alternator and charging system

[SKperformance]

it sounds weird

but what i am saying is

if the battery is not supplied with enough juice befoer the car is turned off

then it car resart the car shortly but after a few hours that ok voltage has now become too low to start as it was never at its full potential

[VMF]

nah, not possible. if the chargin has gone bad then while the engine is running it will take power from the battery as well. thats the way the circuit has been built. so if you shut down the engine and restart immedialty it will not start coz the battery is drained. but if you let it recuperate for a while it will start the engine right away. what he got is the opposite. thats why i'm saying its the shortage. i had the charging problem in my car. took me a while to find out what was going on. i used to do electrical jobs on cars couple of years ago. saw all kinds of problems with this issue

[SKperformance]

ahh you say not possible do you ehh.... ( trying to sound liek that guy from rockie and bullwinkle)

from the engineering of a toyota alternator they all do not have total losses

meaning tey run for a while as it is usually the cuicuitry inside that is opened up by heat added resistance

unless the power steering pump leaks on them causing a good solid short

i have not seen them go otherwise

i have a problem with mine as do many other owners with lexus where it works fine when it wants to but the car can't be left parked for too long as the batery drains right out

which also causes battery failure

when the battery used to be good but because of a low level charge it caused it to be defective

[Taz]

Thanks guys...sounds like either one of your diagnosis could be right. However as you've had a similar problem, Skperformance, I'm beginning to suspect that the alternator is causing a drain on the battery somehow like you described. I guess it could still causing a drain in spite of the fact that it gave a full 14volts reading when it was in at the dealer? They swore that it delivered 14v and all looked fine.

[SKperformance]

i wouldn't call it a drain

but more of an insufficent out put of voltage

at times

and i have had the alt apart at a rebuid shop and everything checked out

as well as the battery and lexus doing there checks as well

[VMF]

as i told above to check charging just connect the volt meter to the battery while engine is running. it will give u exact answer if its bad or not. its not about the alternator yet

[Taz]

as i told above to check charging just connect the volt meter to the battery while engine is running. it will give u exact answer if its bad or not. its not about the alternator yet

But VMF...isn't this essentially how the dealer should have checked out the charging system...with the engine running and all?

Since they got a reading of 14v why should I get anything different? (Not trying to argue with your knowledge...just not sure I understand).

Thanks.

[VBdenny]

Bad cell in the battery. To check, remove the negative terminal while car is running. If it's the alternator, the engine will cut off. I'd bet anything it's the battery, that is so typical A voltage check of the battery when it's warm will probably show it's okay. Most auto parts stores will do a free load test.

[VBdenny]

Go to COSTCO you can get a new battery for around $50. Ain't worth dicking around with

[SRK]

DO NOT remove the battery terminal with the engine running. That will destroy the alternator for sure.

This isn't rocket science, it is an automotive charging system. The battery can be load tested to prove its output capacity. Have that done.

The alternator can be quickly tested for voltage and current output. Have that done.

That's it. One or the other. Maybe both. Diagnose it properly.

Just don't disconnect the battery with the engine running.

[VMF]

DO NOT REMOVE THE connector!! you can kill your ECU!!! never! under any circumstances do this. Denny you too! not on lexus!!! as to the dealer checkups.... i dont really trust them. they dont do s..t! or even if they did sometimes they want you to come back and give em more $$. anyway this is really simple to test and you dont have to pay 100$ hour labor fee for them. the volt meter costs like 20$. so just get it test it and keep it. very useful thing

[VBdenny]

Well, if you guys say so. But I don't believe it. I've done it on many cars with ECU's without ever having a problem or destroying anything. To give an example of a similar scenario, I guess if the power goes off (like if there was a blackout or something) and your computer cut off suddenly, it would destroy your computer? Doesn't happen. I will admit that I've never done it on my Lexus, so you may be correct, but I don't believe it. Anyone else done this?

Should I find myself in similar circumstances, especially under the conditions described in the intial post,, I'd just put a new battery in. Man, they are cheap! All to often, people try to nurse 4 year old batteries along hoping they will come back to life. But we all know that won't happen. My brother sells industrial batteries and charging systems and he has long told me that when they go bad, that is a very common sympton. Put a new battery in (check previous posts on this board, do a search for batteries) and see what happens. Worst case scenario, you'll have a new battery.

Should you need a new alternator, and it's a DIY, have the parts dealer test it before you go home and install it. I always like to see low 14 Volts. If it is in the 12's, don't accept it, because if is inferior. I rejected one that was putting out 13v and the auto parts dudes didn't have any problem with trying another one. I learned this the hard way once. I installed the new POS alternator and it I still had a problem. Reluctantly, I took it back off and I took it back. Well they put it on their machine and it tested out at 11.3v. Then, they gladly exchanged it (which is where the previous statement came from) for another and I went home an gladly reinstalled it :( AGAIN

Maybe I was wrong about the test I suggested, but I've used it on many computer equiped, American made cars. I fosmthing is different, that would mean that the Nippon cars are inferior to American made cars in that respect as they can't lose electrical power without experiencing castastrophic failure of the alternator or computer. I've seen voltage surges destroy electrical components, but I've never seen a loss of electrial power do the same. Not to be rude or anything because I think you guys are great, but........... I still think you are wrong. But hey, better to err on the side of caution. Better safe than sorry I always say. Better believe that I've screwed up more than one thing before, just trying to save a little money.

Denny

Sorry VMF and SK, but we always agree to disagree.......... don't we?

[SKperformance]

i think we all have different opinions not disagree

which is such a strong word

ok enough of the political crap

you guys are all wrong ;)

i am kidding again

i also do not belive and have never seen a charging system cause a problem by disconnecting the battery

it is used to support the system when the engine is off and to start it

nothing else

after the car is running it has no use for the battery except to charge it again

the only concern to have about disconneting it is to make sure you do not hit the poistive side of the battery post as THAT might cause a problem

just my opinion from what i have learned in college as an auto tech

just like the jumping a car battery does not need the donor car to be running

if it can start off that battery why shouldn't yours

it goes against alot of what people have learned ,but information is no good if it is bad information

so who is the first to respond

[SRK]

It is not that disconnecting the battery lowers voltage, or eliminates it, it is that disconnecting the battery removes a huge resistance in the circuit and causes a voltage spike, in that the regulator in the alternator cannot respond quickly enough.

The admonition against disconnecting the battery on a running engine has been around long before computer controls simply to protect the diodes in the alternator. With computers the advice is even more important. The owner's manual, and the shop manual both specifically mention this, as does every service manual I have ever read.

A simple voltage test of the battery will not prove much. An alternator is quite capable of producing a reasonable voltage with one or even more blown diodes. A load test is required. A battery can be quickly tested with a carbon pile load tester. Simply "hanging parts" is not diagnosis. Find out what the problem is and fix that.

I fix automobiles for a very long list of customers. They expect I will diagnose correctly the first time. Not all repair shops are rip-offs. To imply otherwise is simply not being fair.

[ToddLS400]

This sounds like it could be bad contacts in the starter? Does it start up right away after getting a jump or charging the battery? Mine did the same thing until it would take 5-10 min's to just get it started. Then after driving during the day it seemed to start fine if it didn't sit too long. That's the way I bought my LS400 but I got a great deal because of it. If you search my earliest posts (3 or so months ago?) here, you'll see that I thought I had a battery drain as well. I talked to a lot of people on this and I guess the contacts in the starter going out after 100K is common with Lexus. I got the local mechanic to do the job for $350 with labor and parts (replace contacts in starter only). My mechanic is about 200 yards up the road from me. It's nice.

The Lexus dealer will charge you $1,200 to replace the complete starter. Don't use a Lexus dealer to repair your car. They have the Devil's DNA flowing through their blood.

My stupid PS pump is leaking onto my alternator causing it to go out prematurely. I can hear it kind of lightly squeak now and sometimes my battery light comes on. The PS pump over the alternator is a serious design flaw. Especially when most of them seem to leak. I need to build a shroud around the alternator so the fluid doesn't leak ontop of the alternator. Somebody else here did that. The alternator has a lifetime warranty but I have to pay a little for labor from the shop. Changing the alternator is actually a pretty easy job for once on this car.