Charging system voltage drops when revving engine
Instead of increasing with engine speed, the charging system output drops significantly or fluctuates wildly under acceleration, which quickly drains the battery and leaves the alternator buried and difficult to test.
What people tried
Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.
- 1replacing the voltage regulator
- 2cleaning the commutator and brushes
- 3checking all grounds
- 4running without the voltage regulator and testing the generator with a multimeter
In their words
Unedited, most upvoted first, each linked to the thread it came from.
“At idle, I’m seeing about 12–14 volts directly at the generator. As soon as I bring the RPMs up, the voltage drops to around 6–8 volts.”source ↗
“What if I had a similar problem 12v at battery, but stomping the throttle causes the voltage to jump to like 15 before it cuts, battery dies quick... probably alternator? I can't figure out how to test mine, it's too buried.”source ↗
Where this came up
People with this problem also raised
- 3Why is my car revving so high on a cold start?
- 5Why does my car lurch and shake when I accelerate at low RPMs?
- 2New battery still showing low voltage
- 10Why does my car lose power when I step on the gas?
- 8Engine misfires and RPM surging when driving uphill
- 13Intermittent car hesitation with no trouble codes