I own a 2002 SC 430 with 180K miles. It has the original starter and alternator. The battery has been dying, but starts on 1st crank when I get a jump start. I took the battery to Auto Zone and they said it was working at 75%-still good. The battery is 16 months old.

I then took my car to my mechanic (Ex -Lexus Certified Mechanic). He said the alternator needed to be replaced. He installed another alternator yesterday which had 100 amps. The alternator he took out of my car had 130 amps. He said the car seemed to have reduced power when all accessories were turned on.

The problem wasn't fixed. My car will not start after 1 minute of being turned off. The lights, air, ect all work--but the engine still won't start without a jump. The mechanic said it had to be the battery-and to return it to the store and get an exchange.

Anyone know what the issue might be? Do I need the alternator with 130 amps to get my car started? Also, anyone know a solid Lexus mechanic in Dallas? I've driven Lexus' for 15 years and have been spoiled having very few mechanical problems. This is driving me nuts. I'm stumped and frustrated
THANKS in advance, Tony

 

What was the mechanics decision based on regarding the alternator. The alternator sole purpose is to charge the battery. Was you old alternator charging. I believe at idle the battery should read `13.5 to 14 volts while the motor is running. Why would he replace a 130 amp alternator with a 100 amp. The sc-430 has a heavy electrical need. Lots of electronics AC top etc etc. I would find another mechanic or at least varify his diagnosis. Can you get your old alternator back ??

 

Well this raises a lot of questions... Did your mechanic test the battery with a Volt Ohm meter? What was the car drawing with the ignition off? Does he even know how to do it correctly? Did he check the output of the old alternator? A 100 amp is underpowered/rated for the load in THIS car? Why would he install an underrated alternator when you're already having charging issues? Were lights left on? Trunk ajar.. Do you know the rating and group size for the current battery? Do you know what's supposed to be used?
Sadly without answers to these question it's hard to help. It could be a combination of issue...but the undersized alternator is not correct no matter what.

BTW welcome to the forum...there are quite a few threads on battery issues. Here's one that will help you answer some of the questions I posed. SC430 Battery Issues

 

I am currently having the same issue. The battery has only 5k life with 13mos since last replaced. I called AAA for a jump and did a diagnostic test on the battery and the result does not indicate that it is the battery issue. Prior to this issue (won't start unless a jump is required), I had not been driving the car for about 10 days. The AAA mechanic stated I might need to let the engine running for at least 45 mins. I did just that and drove the car for 30 mins. The min i turned off the car and tried restarting it, the car won't start unless a jump start is performed. Can anyone tell me If this is due to an alternator issue or something else? Thanks in advance.

 

You guys might have a starter issue, the battery turns over the starter,the alternator keeps the car running and charger the battery. If u pull the red battery cable while the car is running and the car shuts down then more than likely it's the alternator. So I would advise u to check the starter see if u here a tick or some type of noise when u turn the key over.

 

just curious what would the tick or any noise for that matter indicate? (good or bad)

 

Sometime you get a bad or loose spots on the starter teeth, so while you turn the key you might hear a ticking sound when your trying to start the car. My car did the same thing I heard the ticking noise when I had the door open trying to start my car, I took it to the dealership and found I had a bad starter.