Quote:
Originally Posted by Lug1
13.5V when running is not normal, not good, I disagree with the oldtimer.
Should be around 14.2V.
Unless you have an exotic issue (bad wiring), this sounds like an alternator slowly going bad.
Used Denso (OEM) alt's on ebay are ~$70. I'd put a tested alternator in your truck as first step of diagnostic. Then test the voltage while running, if it's up to 14+V, you found the problem (and fixed it).
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Charging voltage of the alternator depends on temperature. Hotter = lower voltage.
From the Toyota manual:
13.9−15.1 volts with engine running at 2000 rpm and 25°C (77°F)
13.5−14.3 volts with engine running at 2000 rpm and 115°C (239°F)
That temperature is at the alternator rectifier/regulator.
That said, 13.5 at idle should be a bit higher if the engine is the only load (lights off, brakes off, stereo off, HVAC off, etc.). I'm also a bit surprised that the battery resting voltage is 12.4 - it should be closer to 12.6.
-Charlie
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