How can I tell if the alternator needs to replaced? [Archive] - Audi Forums

: How can I tell if the alternator needs to replaced?

11-26-2011, 07:12 PM
Hi folks. New to the forum...

And if it needs to replace replaced, is there a DYI on it in this forum?



11-27-2011, 07:49 AM
Why do you think alt is no good? Is your battery constantly flat? To test it use a multimeter to check the voltage across the battery (poss & neg terminals) with the engine running, you should have between 13.2 & 14.1 volts. If only 12V (not changing running to not running) alternator has had it (as long as belt is on well & wires connected to it properly). Each engine is different as to exactly where alternator is fitted, but all are mounted at the front end of the engine and they are all held on by a couple of bolts, simply unbolt/rebolt. Search the web for a 'how to' for your engine.
Let us know how you get on.

11-27-2011, 09:38 AM
if alt is charging, running 13.2 +, ck batt V's after sitting over night, if batt is 12.25
v's or near, less than 12.50 u need a new battery, advanced or auto zone can ck alt & batt on car - its free. these are just basic tests, but they can ck amp put out & load.
use a digital volt meter

12-02-2011, 09:42 AM
Thanks. Battery is definitely draining each time I try to start the car. Trying to take the alternator of but having trouble figuring out how the tensioner work... Help??

12-02-2011, 12:42 PM
Okay... so got the alternator taken off. Going to Advance Auto to have them test the alternator.
Suggestions and experience on "remanufactured" versus new alternators? Is it worth is to look for the cheapest? Go with Bosch?