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Discussion Starter · #1 ·
My 2008 Tundra Grade 5.7L 4x4 has an unusual alternator problem with 148000 miles on it. When I turn ignition on the battery light will come on and upon start it goes out as normal. I noticed the voltage gauge being between 9 and half way mark which means it was not charging. Voltmeter check confirmed it was not charging. I have researched and checked all associated fuses to be good. I have not checked right at alternator yet as it will be a pain to get to. Has anyone else found the alternator to be bad with the light acting normal? Before I go further I would like to have an alternator to replace on hand if others have had this kind of problem and replaced the alternator and not just bad connections at alternator. From what I read the average alternator lasts only 7-8 years and up to 150000 miles. I have had many cars go over 200k with no alternator problems and wonder if this is just a Tundra problem. Seems to me that charging cable from alternator to the fuse would have a bad joint at alternator since the alternator is telling the light not to come on as alternator is saying everything is fine. I know strange things can happen for it to be a failed alternator and just checking to see what others have found. Also thinking to be preventive and replacing anyway if this is a common problem with Tundra...Thanks
 

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With it running does the volt gauge drop or go higher when you turn on the headlights? Take the truck to an auto parts store and have a load test done on the battery before you start stockpiling "what if" parts. An alternator needs to be "excited" on start-up. Most of the time just driving them gets the job done. When I converted my Model A to an alternator, I always had to give it a little rev of the engine to get it to swing charging.
Welcome to the forum, and remember to ALWAYS "enjoy the adventure"... Chap
 

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Discussion Starter · #4 ·
Any load drops the voltage. The light goes out upon start which makes me think it could be a bad connection at alternator. The light is triggered by alternator output voltage being less than battery so the monitoring system is thinking alternator is working. I just need to check at alternator to confirm what the problem is which is a pain to get to. I have seen a lot of strange things happen with electronics and that is why I posted here to see if others here have had the light go out and be a bad alternator. Thanks
 

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I think Chap's right though. Do the physical searching around you are for obvious signs of something wrong, but I've seen a lot of threads on here where a bad battery created all kinds of weird problems the owner never thought it would have.
A load test is quick and cheap, sometimes free depending on the shop.
 
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