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Voltage regulator is part of the alternator ( on Back), you'd be better off just replacing the alternator, also if you remove and take to have tested at local auto parts store I know Advanced Auto and Auto Zone good chance others will too.
What I've noticed with the tests an auto parts store performs on an alternator is the tests they perform may not get it up to high enough RPM's to where it'll show it failed, so even if it passes, I'd still get a new one, as I'm also sure that's what your problem is. The light coming on is usually an indication your alternator is on it's way out, however before replacing it, make sure your connections at the battery are clean. Corroded battery terminals can also cause this.
I have an intermittent light coming on. And the voltage output difinately decreases when there is a reasonable load on the alt (e.g. lights, A/C fan, etc.). Can here the fan speed going lower. But after driving further at speed, the light will extinguish and she acts right. Advance guys dis an excellent job of testing this considering it's free! Test results show nothing obvious. I've got $175K on my truck and my insticts are telling me the alt (or Volt reg) are about to give in. Battery is new (june) btw. Any thoughts out there?
Fred
Ended up replacing the alternator. Although the 'sheet' from the repair shop listed alt replacement as the fix? On the copy of the handwritten mechanic's assessment, he listed it as a regulator failure. I took it in after I started getting voltage spikes (yes, high voltage) as opposed to the low voltage symtoms it was exhibiting. Funny, the tech said that it would pass the test sometimes...Weird.
Ended up replacing the alternator. Although the 'sheet' from the repair shop listed alt replacement as the fix? On the copy of the handwritten mechanic's assessment, he listed it as a regulator failure. I took it in after I started getting voltage spikes (yes, high voltage) as opposed to the low voltage symtoms it was exhibiting. Funny, the tech said that it would pass the test sometimes...Weird.
Yep, that's what I told you, don't trust the test.