Alternator ground

[chrisca70]

I'm diagnosing the common battery dimming light on my cluster.

- I did the easy and cheap fix and replaced the alternator voltage regulator
- Changed the engine ground cable (the one that goes from the oil pan to the chassis).
- Battery with the car off is 12.5v, so it's fine.
- When I turn the car on the battery drops to 11.5v

All this points to a faulty alternator, will take it to auto zone for final confirmation today.

Also the RealOEM diagram shows an alternator ground cable. My alternator did not have this cable.

Does anyone know where should I attach this cable to? (#6 in the attached diagram)

[jlevie]

Before bothering to add a ground cable, which is only needed on alternators that have rubber mount bushings, Use an ohmmeter to check the resistance from the alternator body to a chassis ground point. That should only be an ohm or so. If the resistance check is okay, there is another problem.

[chrisca70]

Great point, my alternator has no rubber mounts, it's all metal to metal, so is grounded via its own metal mounting points. A ground cable is not needed then.

Will check that resistance just in case. - Thank you!