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Pete, Technician
Category: Lexus
Satisfied Customers: 27126
Experience:  Over 17 years diagnosing and repairing automobiles various makes and models with some training and certifications.
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I have a 2000 ls400, my alternator went out, so i had a shop

Customer Question

hello, i have a 2000 ls400, my alternator went out, so i had a shop rebuild my oem to higher output 200a. I installed new one, worked perfectly for 1 week, then would not charge, i removed alternator, had bench tested, tested good, reinstalled, voltage meter in place,, started, worked for 20 seconds and with clicks in hood fuse box, battery slowly drained to 10.2 volts while idling. After that, it would not show the brief charge, I uninstalled alternator, checking oem wiring, reinstalled alternator, got 20 seconds of charging again, then battery drain to 10.2v.
I brought back to shop that rebuilt it, i explianed voltage regultor will woprk on bench test , because its been disconnected, brought car in. alternator never showed a charge, they even bypassed my car with the 3 wire harness and plugged into their bench test machine, it didnt work. so they built me a new alternator. I just installed and it doesnt work, did not even get the 20 seconds of charge, im losing my mind, i replaced 120a fusable link fuse, the 40a fusable link fuse. the only thing i can think of is a relay gone bad or a circuit breaker that im unaware of.
JA: Does the battery look like it's leaking? And does it have a strong smell -- like sulfur?
Customer: new battery
JA: What is the model of your '00 Lexus?
Customer: LS400
JA: Are you fixing your vehicle yourself? What have you tried so far?
Customer: its in the 1st message i sent
JA: Anything else you want the mechanic to know before I connect you?
Customer: this doesn't seem possible, this whole thing, i cant wrap my head around this
Submitted: 8 days ago.
Category: Lexus
Expert:  Pete replied 8 days ago.

My name is ***** ***** I am a professional here at Just Answer. I noticed that your question had not received a response and thought I would see if you still need help with this.I apologize for the delay and I hope I can still assist you with this here.

Inspect the wiring leading to the alternator for any issues.If any issues are found with the wiring this will have to be repaired to resolve this fault here.If all wiring is checked and found to be o.k. let me know so we can continue.

If more help is needed, use the reply tab to continue our conversation. If no further assistance is needed, kindly rate my service,your 5 star rating is appreciated.You can rate at any time and we can continue to work on your question as this will not close out your question.Keep in mind in some cases it can be difficult to fully diagnose or help repair your vehicle without seeing it and I work on delivering the best possible answer from what I see to work with.

Thanks Pete

Customer: replied 8 days ago.
already done, i replaced the pigtail and shop confirmed connection is good
Expert:  Pete replied 8 days ago.

Do you have a test light or multi meter to test with at all?Is it in the vehicle now and acting up?

Customer: replied 8 days ago.
i have to charge my battery, it took a new battery down to 10% idling
Expert:  Pete replied 8 days ago.

O.k.,when it is charged up locate the black/red wire and the white/light blue wire at the alternator and with the engine running see if these two wires have 12 volts DC on them with the ground lead of the meter connected to the alternator chassis for a ground signal.Then test the blue power feed wire from the alternator and see if it has around 12 to 14 volts with the engine running and let me know.Let me know what you come up with here when your ready.

Thanks Pete

Customer: replied 8 days ago.
test those 2 wires with the plug disconnected from the alt?
Customer: replied 8 days ago.
or poke at rear of pigtail in each wire feed to get a connection?
Expert:  Pete replied 8 days ago.

You can test the two wires with it plugged in back probing them.

Customer: replied 7 days ago.
It's been a frickin monsoon around here. I haven't had an opportunity to get some dry weather to take some readings. I apologize. I'll let you know asap. I'm hoping soon. Thank you
Expert:  Pete replied 7 days ago.

No problem

Let me know when you are ready.

Thanks Pete