Alternator tests bad, no battery light
Thread Starter
Driver School Candidate
Joined: Jan 2017
Posts: 1
Likes: 0
From: OK
Alternator tests bad, no battery light
Battery on my 03 430 has been dead the last two mornings. Tester at parts shop shows a good battery but bad alternator/voltage regulator. Voltage reading with when running/lights on bounced a bit between 13.3-13.7.
Planning to replace the alternator, but wondering why I'm not getting a battery warning light on the dash. Any other issues I should look out for in this situation?
Planning to replace the alternator, but wondering why I'm not getting a battery warning light on the dash. Any other issues I should look out for in this situation?
Lead Lap
Joined: May 2006
Posts: 3,682
Likes: 304
Battery on my 03 430 has been dead the last two mornings. Tester at parts shop shows a good battery but bad alternator/voltage regulator. Voltage reading with when running/lights on bounced a bit between 13.3-13.7.
Planning to replace the alternator, but wondering why I'm not getting a battery warning light on the dash. Any other issues I should look out for in this situation?
Planning to replace the alternator, but wondering why I'm not getting a battery warning light on the dash. Any other issues I should look out for in this situation?
Instructor
Joined: Jan 2018
Posts: 976
Likes: 301
From: WA
There was a thread on this board about changing the brushes in the alternator a while back. I would investigate that possibility before replacing the entire alternator. In many cases a "bad alternator" can be repaired for under $ 10 by simply replacing the alternator brushes. Brushes do wear out eventually. I believe there is also a YouTube video showing the procedure.
Instructor
Joined: Dec 2015
Posts: 878
Likes: 232
From: Arizona
Your voltage is correct for these cars. A bad voltage regulator will either have very high or low volt output. Have the alternator tested for amp output as this is what actually charges the battery. If it checks out you have a bad battery even though the auto parts store says it's good. I did an alternator rebuild on this site a few months ago if you want to fix it yourself.
Intermediate
Joined: Dec 2018
Posts: 302
Likes: 30
From: Washington
Amp clamp?
Very handy tool. May be.difficult.to isolate.the alternator. Coming directly off the alternator you are lookng for AC amperage, If the voltage regulator is external it's not hard at all. I routinely check motorcycle stators this way. Regulator is always external on bikes I have worked on.
Driver School Candidate
Joined: Aug 2019
Posts: 1
Likes: 0
From: md
My indicator light came on and immediately thought I had a bad battery....was able to get the 5 miles to home, had AAA check the battery but was told it was OK........battery died very quickly after. Had it towed to a Lexus dealership and they replaced the alternator. Very expensive repair on my year model as the alternator is very difficult to get to....5 hour job.....$1375.00!!!!!
my suggestion is don’t drive on it...get it fixed right away....me battery died within minutes of getting the indicator.
my suggestion is don’t drive on it...get it fixed right away....me battery died within minutes of getting the indicator.
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Lead Lap
Joined: May 2006
Posts: 3,682
Likes: 304
As mentioned above, our alternators can fail, but not very often. Make sure your alternator is at fault before changing. Many owners mention their alternators putting out in the 13.4-13.8 volt range which is normal. Don't let that be the deciding factor in replacement. My alternator has always put out 13.4 volts (with lights, a/c, defroster, etc on) since I purchased it 10 years ago. I've never had a problem with my charging system or starting my car.
Last edited by Bocatrip; Oct 4, 2019 at 06:48 PM.
Instructor
Joined: Jun 2019
Posts: 1,056
Likes: 210
From: Florida
[QUOTE=dontcallme;10510721]Battery on my 03 430 has been dead the last two mornings. Tester at parts shop shows a good battery but bad alternator/voltage regulator. Voltage reading with when running/lights on bounced a bit between 13.3-13.7.
Planning to replace the alternator, but wondering why I'm not getting a battery warning light on the dash. Any other issues I should look out for in this situation?[/QUOTE}
Sorry for your trouble. Maybe these may help?
Diagnose Charging Issues
How to identify and locate a parasitic drain
Planning to replace the alternator, but wondering why I'm not getting a battery warning light on the dash. Any other issues I should look out for in this situation?[/QUOTE}
Sorry for your trouble. Maybe these may help?
Diagnose Charging Issues
How to identify and locate a parasitic drain
CL Community Team
Joined: Dec 2005
Posts: 2,725
Likes: 837
From: 565 St Peter NOLA
[QUOTE=430SLOwner;10627991]
Sorry for your trouble. Maybe these may help?
This thread was started 5 months ago, I'd like to think he's fixed it by now...
Sorry for your trouble. Maybe these may help?
This thread was started 5 months ago, I'd like to think he's fixed it by now...
Last edited by bradland; Oct 4, 2019 at 09:51 PM.
My indicator light came on and immediately thought I had a bad battery....was able to get the 5 miles to home, had AAA check the battery but was told it was OK........battery died very quickly after. Had it towed to a Lexus dealership and they replaced the alternator. Very expensive repair on my year model as the alternator is very difficult to get to....5 hour job.....$1375.00!!!!!
my suggestion is don’t drive on it...get it fixed right away....me battery died within minutes of getting the indicator.
my suggestion is don’t drive on it...get it fixed right away....me battery died within minutes of getting the indicator.
Instructor
Joined: Jun 2019
Posts: 1,056
Likes: 210
From: Florida
Intermediate
Joined: Nov 2013
Posts: 310
Likes: 35
From: Minnesota
I replaced my alternator about a month ago. I was driving on the highway and the car would intermittently shut off while doing 70. Also, the rear inner taillight would sometimes flicker or turn off completely which I thought was weird, and it had been doing that for a while but I never would have tied that to the alternator. I replaced the alternator with one from Autozone for two reasons. For one, it was on sale, and for two it has a lifetime warranty and the alternator wasn't that bad to replace at all so even if this one fails within two years its not a big deal for me to get under there and replace it again. Plus it'll give me a reason to work on the car. 
Aaaand here come the comments about "You should've replaced it with OEM Denso, what are you thinking?" and "Have fun replacing that in a week". Feel free to fire away at me..... or be positive?
Aaaand here come the comments about "You should've replaced it with OEM Denso, what are you thinking?" and "Have fun replacing that in a week". Feel free to fire away at me..... or be positive?
Last edited by westopill; Oct 5, 2019 at 10:33 PM.
Lead Lap
Joined: May 2006
Posts: 3,682
Likes: 304
I replaced my alternator about a month ago. I was driving on the highway and the car would intermittently shut off while doing 70. Also, the rear inner taillight would sometimes flicker or turn off completely which I thought was weird, and it had been doing that for a while but I never would have tied that to the alternator. I replaced the alternator with one from Autozone for two reasons. For one, it was on sale, and for two it has a lifetime warranty and the alternator wasn't that bad to replace at all so even if this one fails within two years its not a big deal for me to get under there and replace it again. Plus it'll give me a reason to work on the car.
Aaaand here come the comments about "You should've replaced it with OEM Denso, what are you thinking?" and "Have fun replacing that in a week". Feel free to fire away at me..... or be positive?
Aaaand here come the comments about "You should've replaced it with OEM Denso, what are you thinking?" and "Have fun replacing that in a week". Feel free to fire away at me..... or be positive?