1998-2000 ls400 alternator upgrade
04-28-20, 02:13 PM
#46
Racer
So my 98 seems to have a dying alternator. I am looking at this Mechman Alternator like this thread suggested. My alternator is only putting out 11V and dropping to like 9.5V. When the car starts the reading will jump to 14.3 but no matter how much driving I do the alternator will never charge up. Its possible my alternator or some wires are corroded and a bad ground or connection somewhere is my issue.
Alternators are designed to maintain and slightly charge batteries. However if the electrical load exceeds the alternator capacity it'll drain batter. I'd use an external battery charger for dead or near dead batteries
Got one from harbor freight worked great when I discharged my battery to drive it home when my alternator died
Was meant for you not bradland
04-28-20, 05:46 PM
#47
Intermediate
Not sure what you mean here- the alternator doesn't "charge up" it simply produces power for the cars electrical accessories while driving and maintains the healthy state of the battery. If the battery is on it's last leg the alternator will not be able to charge it sufficiently. The primary purpose of the battery is to hold a charge powerful enough to start the car, once the car is started the alternator does all the work.
Why do you need a 240 amp alternator?
Why do you need a 240 amp alternator?
04-28-20, 05:49 PM
#48
Racer
Well I had those weird electrical gremlin in this 98 that have seemed to die. Now the car just won't start, takes 10 minutes of trying to get it to finally start, but once started will run/drive forever. When I first turn the key to ON my the car reads 11V, when it should be 14. Electrical stuff in the dash always turns back on like the battery has been dead. The radio won't always work. Might drop to 9.5 before the car starts. When I had it boosted after the winter CAA guy told me battery is ok, alternator is not. And now I can hear what I believe is alternator whine from the engine. Local Toyota want $450 plus tax for the alternator alone and then up to 5 hours for labor. Can only buy rebuild Denso otherwise. I just thought this would be better.
04-28-20, 05:51 PM
#49
Intermediate
That would test what? If its the alternator? I may have meant the alternator is not charging the battery enough. I was told the Alternator is not putting out enough power. I was hoping that by driving the car around and letting it run for along time would help the alternator but nope.
04-28-20, 05:54 PM
#50
Intermediate
Ok thank you Sin. That is what I thought. I don't know how I missed that it was so low before. I was so focused on the starter.. could be because when the car starts it jumps to 14.3 and I saw that. I may try and replace it myself... I have seen the thread and some videos... You have to take apart many things but I have time.
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Sin1UZFE (04-28-20)
04-28-20, 05:55 PM
#51
Racer
That would test what? If its the alternator? I may have meant the alternator is not charging the battery enough. I was told the Alternator is not putting out enough power. I was hoping that by driving the car around and letting it run for along time would help the alternator but nope.
When I got my ls the ps pumo was leaking and leaked onto the alternator. Replaced the pump and cleaned the alternator with brake clean. Ran great for a year. Pumped out 14.4 or 14.6v then in a drive through battery light came on got back to office. Used coworker multimeter saw 12.6v when car was off. 10.6 or so when on. Got it home, pulled neg while on. Car died. Ordered reman denso, installed it a week later. Back to 14.4v or so.
04-28-20, 05:57 PM
#52
Racer
Ok thank you Sin. That is what I thought. I don't know how I missed that it was so low before. I was so focused on the starter.. could be because when the car starts it jumps to 14.3 and I saw that. I may try and replace it myself... I have seen the thread and some videos... You have to take apart many things but I have time.
04-29-20, 06:45 AM
#53
Pole Position
So my 98 seems to have a dying alternator. I am looking at this Mechman Alternator like this thread suggested. My alternator is only putting out 11V and dropping to like 9.5V. When the car starts the reading will jump to 14.3 but no matter how much driving I do the alternator will never charge up. Its possible my alternator or some wires are corroded and a bad ground or connection somewhere is my issue.
Then the battery wont take and hold the charge from the alt.
I would take the battery to one of the chain parts stores and have them put the battery on a charge, and they will tell you if it's good or not. Alot easier pulling the battery out for a test instead of the alt. Being only a year old doesn't always mean it's still good. I've heard of some batteries only lasting 6 months. Hope you got a warranty on your battery.
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400gs99 (12-11-21)
04-29-20, 08:02 AM
#54
Intermediate
It sounds to me like your battery is bad and alt. is good. You say your "alt" is putting out 11v and drops to 9.5v. I think you mean your "battery" cuz when starting it your starter is pulling the power out of the battery, not the alt. Then when it starts (Alt spinning and charging) goes to 14.3. (perfect) Exactly what it's supposed to do.
Then the battery wont take and hold the charge from the alt.
I would take the battery to one of the chain parts stores and have them put the battery on a charge, and they will tell you if it's good or not. Alot easier pulling the battery out for a test instead of the alt. Being only a year old doesn't always mean it's still good. I've heard of some batteries only lasting 6 months. Hope you got a warranty on your battery.
Then the battery wont take and hold the charge from the alt.
I would take the battery to one of the chain parts stores and have them put the battery on a charge, and they will tell you if it's good or not. Alot easier pulling the battery out for a test instead of the alt. Being only a year old doesn't always mean it's still good. I've heard of some batteries only lasting 6 months. Hope you got a warranty on your battery.
04-29-20, 08:11 AM
#55
Pole Position
I was about to buy a new battery for it and the CAA guy said the battery was good. From the reading he got from the portable booster anyways. After the car started he said maybe its the battery, but I thought he was joking...When I buy a battery I will get a warranty for sure. Thank you.
04-29-20, 08:33 AM
#56
Intermediate
Yea, I would get a second opinion on the battery. Understand those warranties, they say 3 or 5 years but most of them get prorated after 1 year. If it goes bad after 1 year then you would have to pay on a new one for the time you used the old one. It'd still be cheaper though.
Edit: Also the last couple of times the car got started it didn't jump to 14.3, it only went to 11.8 or 13.4 or something like that. The battery and ALT could both be shot.
Last edited by JohnAndic; 04-29-20 at 08:55 AM.
04-29-20, 02:31 PM
#57
Racer
CAA has a good warranty system if you buy the extended warranty. The thing is the car won't start right away even if on a booster pack. And I can hear a whine from the engine that I believe is the ALT. A bad battery won't cause alternator wine will it? A google search tells me I guess it could be. If the alternator is sending more power then it should be because the battery is bad. But this is just with the car in the ON position. A new battery is a good place to start I guess. The battery did have a good amount of leakage/corrosion when I bought the car.
Edit: Also the last couple of times the car got started it didn't jump to 14.3, it only went to 11.8 or 13.4 or something like that. The battery and ALT could both be shot.
Edit: Also the last couple of times the car got started it didn't jump to 14.3, it only went to 11.8 or 13.4 or something like that. The battery and ALT could both be shot.
04-29-20, 03:12 PM
#58
Intermediate
Right now it seems like giving it a little gas helps it to start at first. I may take the engine apart as much as I can see if I can find anything. I may take it to Canadian Tire and buy a battery and get them to inspect it and see what they say. Or I may take it to Lexus for an inspection and see what they say. But any comments/help is appreciated.
04-29-20, 03:14 PM
#59
Racer
Today it was 14.4 from the reading direct from the battery. Yes it stays at 14.4, 14.3 once going I think, I only have a plug in tool that tells me me the Voltage right at start-up. I know that once the car is shut off at 14.4 it won't be 14.4 when you turn it back to ON right away. I just had CAA here to buy a battery and he tested it. It was reading 14.4, he said the ALT was ok but the Starter was bad. I thought it was the starter at first but I dunno. The car starts fine eventually. It gives the one click but wont struggle at all when it won't start. When it eventually starts and gets driven it starts back up way easier so I was leaning back towards battery. The CAA guy didn't want to sell me a battery because he thought the starter was bad so I didn't get one but I'll get it elsewhere.
Right now it seems like giving it a little gas helps it to start at first. I may take the engine apart as much as I can see if I can find anything. I may take it to Canadian Tire and buy a battery and get them to inspect it and see what they say. Or I may take it to Lexus for an inspection and see what they say. But any comments/help is appreciated.
Right now it seems like giving it a little gas helps it to start at first. I may take the engine apart as much as I can see if I can find anything. I may take it to Canadian Tire and buy a battery and get them to inspect it and see what they say. Or I may take it to Lexus for an inspection and see what they say. But any comments/help is appreciated.
The fact that it starts right away with a booster should tell ya it is the battery. Go to Walmart get the $90 24f they got...that's what I use. Cranks strong.
04-29-20, 03:30 PM
#60
Intermediate
What does the battery read when car is off? Should be around 12.6v. it's normal to drop while cranking and should go to 14v when on. 14v when on means good alternator if it was lower then bad alt. Sorry I misread your posts.
The fact that it starts right away with a booster should tell ya it is the battery. Go to Walmart get the $90 24f they got...that's what I use. Cranks strong.
The fact that it starts right away with a booster should tell ya it is the battery. Go to Walmart get the $90 24f they got...that's what I use. Cranks strong.
It won't start right away with a booster. Acts the same with or without booster, unless the battery is completely dead. I may not have been clear.
The new resting Battery reading from the cigarette is 9.5. I just went to start her up. Was sitting at 9.5. She started on the first crank because it was running earlier I think. On start-up reading goes to 14.3. After Idle for a couple minutes and turn off. turn back to ON right away, reading is down to 12.1.
I could put a new battery in and experience the same issue when starting at first. I could have a parasitic drain. A new battery is the first step to finding that out. If a new battery fixes the starting issue and keeps a charge then I'm possibly home free.