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YOUR RESEARCHAlternator Voltage
Leading reported evidence
Check voltage
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Performed · outcome unconfirmed · Original poster
I have checked my voltage with a good quality meter and it agrees with the gauge, so I doubt it's an instrumentation error.
Leading evidence: 'Check voltage' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Check specific model' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Suggestion
Often it is just the diodes that fail.Lots of Youtube videos =Check for your specific model
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Suggestion
And the voltage will go up when the engine is running faster than idle.
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Rennlist: 1 discussions
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Generation: 20261026T163944Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
I have a 2002 C2 with 77.700 miles, and my alternator recently went south. I purchased a 997 150 amp replacement, new from Bosch, and found that this was the same model of alternator that had failed. I was expecting a 120A unit.
The old alternator output 13.75V when operating, and the new one is a bit higher, at 14.0V. At first, I attributed this to the time I was likely operating the car with the bad alternator, but I've put about 25 miles on it since replacing the alternator, and the voltage remains slightly higher than it had been previously.
I have checked my voltage with a good quality meter and it agrees with the gauge, so I doubt it's an instrumentation error.
So, to the group, what voltage does your charging system indicate when driving at 3K RPM?
All depends on what loads you have on while driving, mine is around 13.5 to 13.7 with auto on with a/c heater, you are good with up to 14.7 V charging. I plan to use the same alt. when my alt. goes out.
At cold start with no load such as a/c, low beam, etc it's 14 to 14.1v. The voltage then starts to taper to 13.5 to 13.8v once you have driven some distance. The more discharged your battery, the colder the ambient temp, the longer it stays at close to 14v.
With some load such as a/c plus low beam, the voltage should stay above 13.5v regardless of rpm.
Alternator voltage should go up as the battery charges over time. It also goes up as the load on the system goes down. The max voltage when there is no load should be in the 14v range, with 14.4v for most cars. Anything higher approaching 15v or more will overcharge the battery and result in shortened battery life. With the car running and having a lot of draw (heated seats, lights, stereo, and other accessories on), you should see the voltage drop, even below 14v at idle. And the voltage will go up when the engine is running faster than idle.
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