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.
Found another way around this?
Share your steps and trade-offs so fellow engineers don't have to reinvent the wheel. No account required.
- 1replacing the voltage regulatorDid this help you?
- 2cleaning the commutator and brushesDid this help you?
- 3checking all groundsDid this help you?
- 4running without the voltage regulator and testing the generator with a multimeterDid this help you?
- 5Replacing the alternator, battery, and belt tensionerDid this help you?
- 6Checking and tightening all battery and alternator connections and groundsDid this help you?
- 7Inspecting the belt installation, wear, and tensionDid this help you?
In their words
Unedited, grouped by where they were said, most upvoted first within each place, 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
- 2Does high RPM driving actually damage your engine?
- 6Why is my car revving so high on a cold start?
- 2Engine RPM drops right after starting unless I give it gas
- 9Car shakes at high speeds even with good tires and alignment
- 4Why do RPMs jump while holding a steady accelerator?
- 7Why does my car lurch and shake when I accelerate at low RPMs?