Hi all, im having some real issues with my charging system and i thought id ask someone who knows more than I before dropping more money on parts. Ill try and be brief, I drive an 01 GS430 and essentially my alternator is not charging my battery anymore. I originally thought it was the alternator, i pulled it out and took it to autozone and had it tested and they told me it was good so i bought a battery instead because i learned my old one was bad. Installed old alternator and new battery. It drove for about 20minutes and battery light came on. I plugged my little charging system tester into my cigarette lighter and it says alt voltage low... I went home and thought about another possible solution is doing the Big3 upgrade. So i did just that. I ran 2awg wire from positive on alt to inline fuse to pos on batt, 2awg ground from ground on alt to chassis to neg on batt, another 2awg ground from neg on batt to chassis, and last i ran 2awg ground from motor to chassis. That should do it right? Wrong. Still same problem, the battery light comes one after about 10 minutes of driving and battery dies from there. Im sure i am looking over something maybe but i just think its a bad alt. Please any help or advice would be awesome to have and greatly appreciated. Thank you all and sorry for the post if it seems rambling.

 

Can I assume your alternator pig tail connector is broken like almost all others from over the years? if so, what have you done to ensure the connector is seated properly on the back of your alternator?

 

As far as i recall it was still intact with all wires, just pretty coverd with grease. I could be wrong though you never know. All i did was wipe it off best i could with a shop rag and clicked it back into place. Ill take a better look at it in the morning because i dont have a garage or shop and its frigid as a mother outside rn. Thanks for the tip man.

 

Have you measured the voltage at the battery terminals with engine off and again when running? Should be about 12.6 VDC when car is off and 14.2 - 14.5 VDC when the engine is running and under load (accessories running) at about 2500 rpms. If the voltage is much lower than this when running then your alternator is done. Is it the original Denso alternator? If so, I'd say it had a good run. I recently has similar issues on my 99 GS300 and replaced bad battery first only to have issues remain. Two shops told me my alternator was good. Then I used my trusty voltmeter and did the measurements and found it was charging very marginally. Replaced alternator myself and all issues went away. Good does not always equal Good I find when using outside shops. Also check positive terminal connection on alternator that it is clean, conductive and tight. Check continuity between battery + and positive terminal on alternator. Like others mention above also check the connector to the alternator which is the ECU regulating the alternator output. I assume you checked all charging circuit fuses as well.

 

You should check the alternator fuse, all your fuse while you're at it. Here are some PDF that might help you.

 

Ho Tiamville, where are you finding these PDFs? Is it the Lexus service manual / workshop manual?

 

It's a GS300/400/430 complete dealer service manual.

 

You have tons of accurate information there, thanks for sharing it with us as needed.