E46Fanatics - View Single Post - Voltage issue, need help determining if alternator problem
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Old 01-08-2013, 11:34 PM   #16
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Join Date: Jan 2006
Location: Cyprus
Posts: 6,604
My Ride: ESS TS2 320ci
Originally Posted by dmax View Post
It will take a few seconds after a start to register 14V on the cluster...you're fine there.

I also think something is loose or corroded...ground, battery cable, cable under the +terminal under the hood.

But, tell him if the battery light flashes again and increases its frequency until it's on all the time, that he needs to get home right away because he's driving on battery alone.

Will check all connections over the weekend

Originally Posted by lcoleman View Post
Those symptoms could also be attributed to a bad wheel speed sensor and the known taillight grounding issues.
I fixed his tail light grounding issue a few weeks ago, problem was there before and after. Wheel speed sensors don't trigger a fault code?

Originally Posted by mkodama View Post
An E46 alternator shouldn't be troubled by turning on all the accessories, nor charging the battery after starting the car(the jump to 14.0 volts should take less than a second). The battery looks relatively healthy by the voltage it provides without the engine running, but the varying alternator output seems off. I'd look into fixing the alternator and getting a solid 14.0 volts before looking into the rest, since everything else mentioned will be negatively affected by a reduced output alternator.
Takes a good 10-12seconds to go from 12.5v to 14v

Originally Posted by taibinhvuong View Post
The numbers looked normal to me except that the alternator should not need to take time to reach its max 14.1V, but don't just assume that the alternator is bad yet, it could be either one, a weak or bad battery could also load down your alternator charging voltage to 13.7v with heater and lights on.

The easier way and proper way to troubleshoot the problem is to external recharge the battery overnight or even consider borrowing a known good battery and test it out, from there you can pin point weather the problem is the alternator or the battery, thus save you time and money.
Cheers! will come back with the findings
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