I have had several jump starts yesterday. Autozone tested, told the alternator's peak AMP was like 47 to 51 ( he did the test twice for me ). Is the alternator going bad? Or should I have the drive belt tighten a bit first? I had my local Toyota dealer replaced timing belt, drive belts in December. I tested the output voltage when engine was runing, it was between 14.2v to 14.5v. The voltage seems like normal. The battery testing result is : rechage and retest. It did not
say it was bad. Seems that the battery was not fully charged at least. Any inputs?

 

Your charging seems on the money... the battery has gone bad, I'd consider replacement. It's a build type 24F. The "recharge and retest" is the canned failure for a battery that won't maintain a charge. It was my failure on the replacements with my '84 Landcruiser. The battery lasts for about 34-38 months here in the heat of summer.

 

I had the Autozone recharge my battery today. And the test result was 'good' after charging. So the battery should be fine. Maybe my alternator is going bad...

 

have them test the alternator again, when they put a "load" on it, it shouldnt drop below a certain voltage.

 

Just change the alternator with belts ( if they are old ) . I guess it is easy to change the alternator yourself . I did for Nissan , but never for lexus . It should not be difficult because it looks to me easly accessable .