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Ron Z.
Ron Z., - Lexus Tech -
Category: Lexus
Satisfied Customers: 19026
Experience:  18+yrs experience. State Inspector and Lexus Diagnostics
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I'm trying to figure out whether it is the alternator or

Customer Question

I'm trying to figure out whether it is the alternator or alternator fuse which is responsible for the battery not charging on my 1997 Lexus ES300.
JA: Lots of things can cause problems with the battery. The Lexus Mechanic will know what to do. Tell me a bit more about what's going on so he can help you best.
Customer: I thought the old battery was not taking a charge, and so bought a new one this morning. The battery dash light came on as I was pulling out. Determined that the issue was not the battery but the charging. Hence I am trying to pull the fuse to see if it is blown. Fuse top is clear, so I can see the link is intact, but I don not know if a break could be a hidden condition.
JA: Are you hoping to fix this yourself?
Customer: If it is just a matter of replacing the 100A fuse. most likely. If the alternator is the issue, that is beyond my abilities.
JA: Is there anything else the Lexus Mechanic should be aware of about your Lexus?
Customer: Nothing related to this. It is a great car, now pushing 290,000 miles.
JA: OK. Got it. I'm sending you to a secure page on JustAnswer so you can place the fully-refundable deposit now. While you're filling out that form, I'll tell the Lexus Mechanic about your situation and connect you two.
Submitted: 1 year ago.
Category: Lexus
Expert:  Ron Z. replied 1 year ago.

If you can see that the filament inside the fuse is in tact, then the fuse is good. If it were to be blown, you'd see a noticeable break in the filament, and many times a slight burn mark on the inside of the plastic housing. If you suspect the Alternator is the root of the no-charging problem (which it sounds like it is) there is a quick and easy test for this with the use of a volt meter. With the engine running, take a voltage reading at the battery terminals. If the voltage is not between 13.2-14.4v, or fluctuates in and out of this area, the Alternator will need to be replaced. If you do not have access to a voltage meter, most local "big chain" parts stores, like AutoZone, will run these tests for Free right in their parking lot (except in California). If my answer has helped you, please help me by leaving a rating or accepting my answer so I may be credited. Rating or accepting my answer does not cost you extra. It allows me to be credited for my work. Please rate or accept. You can ask follow-up questions after you rate or accept.

Expert:  Ron Z. replied 1 year ago.

Hi! I noticed this thread was still open and wanted to check in and see how you made out. Was the alternator the problem? Did you have any other questions on this issue?