Alternator: should I replace?
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Alternator: should I replace?
So my 2013 Lexus GX460 left me stranded today. Dead battery after just driving it normal for 20 minutes at freeway speeds and turning it off. Tried to restart about 20 minutes later. No battery. I got a jump then, when at home, I tested the 3 year old interstate battery with a load tester, tested ok, not great, very low end of OK. Also tested the DC Voltage at idle and revving. 13.6 at Idle, 13.75 at 3K revs. I talked to a Lexus tech who said the DCV supplied is low but maybe not ready for a replacement yet. To me, if it is not supplying 14.4V then it is not adequate.
Your opinion? (because I am on the fence for a $450 replacement unit)
Your opinion? (because I am on the fence for a $450 replacement unit)
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The fact that you drove home after a jumping a dead battery suggests that the alternator is working.
The SM says voltage between 13.2V to 14.8V @ 2000 RPM is within spec. The fact that you drove home after a jumping a dead battery suggests that the alternator is working.
I would replace battery, it may be on its last leg.
Also tested the DC Voltage at idle and revving. 13.6 at Idle, 13.75 at 3K revs.
I tested the 3 year old interstate battery with a load tester, tested ok, not great, very low end of OK.
Last edited by mike202; Mar 27, 2026 at 06:10 PM.
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So my 2013 Lexus GX460 left me stranded today. Dead battery after just driving it normal for 20 minutes at freeway speeds and turning it off. Tried to restart about 20 minutes later. No battery. I got a jump then, when at home, I tested the 3 year old interstate battery with a load tester, tested ok, not great, very low end of OK. Also tested the DC Voltage at idle and revving. 13.6 at Idle, 13.75 at 3K revs. I talked to a Lexus tech who said the DCV supplied is low but maybe not ready for a replacement yet. To me, if it is not supplying 14.4V then it is not adequate.
Your opinion? (because I am on the fence for a $450 replacement unit)
Your opinion? (because I am on the fence for a $450 replacement unit)
Thread Starter
Driver School Candidate
Joined: Jul 2024
Posts: 16
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The fact that you drove home after a jumping a dead battery suggests that the alternator is working.
The SM says voltage between 13.2V to 14.8V @ 2000 RPM is within spec. The fact that you drove home after a jumping a dead battery suggests that the alternator is working.
I would replace battery, it may be on its last leg.
The SM says voltage between 13.2V to 14.8V @ 2000 RPM is within spec. The fact that you drove home after a jumping a dead battery suggests that the alternator is working.
I would replace battery, it may be on its last leg.
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6th Gear
Joined: Aug 2025
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From: Massachusetts
Battery issue
I would definitely check for a parasitic draw first. If it's within spec > 50ma, I would recommend upgrading your battery. Lexus has 710 CCA battery that fits perfectly. I live in the northeast. It definitely helped during the winter. Another test to try, don't raise the RPM'S, check battery voltage at idle with as many electrical systems turned on as you can. All the lights, radio, rear glass/mirrors, and blower motor on high. If you are at 12v your alternator is fine.
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I see my DC V+ in the 12.9v-13.5v range - your 13.6v is not "Low" in any way. 14.4v was a standard a while back with "dumb" regulators, but not really a modern standard due to CAFE and fuel efficiency BS (they just have the alternator regulated tightly - just enough to supply running current, and to charge the battery as not to increase parasitic engine power draw via the drive belt). Surprised a seasoned mechanic told you to expect 14.4v on a "Modern" vehicle...
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Originally Posted by DanTeSlagX;[url=tel:12057653
12057653[/url]]Any aftermarket remote starters or hardwired dash cams?
interstate is a good battery but they are not what they used to be. I wish we could get OEM Panasonic batteries in the USA.
interstate is a good battery but they are not what they used to be. I wish we could get OEM Panasonic batteries in the USA.
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