Altenator's

[james 1992 940]

Just a sugestion, but could a number of us note in what we're getting off our alternators?
Mine was running at 13.8 - 13.9 V recently and I believe this to be about correct but I'm by no means certain

[narc]

Lead acid car batteries are usually charged at between 2.26 and 2.36V per cell so for a normal 12V car battery with 6 cells that would give a "normal " range of 13.55V to 14.16V. If you go much above the top value you risk the battery gassing off, much below and the battery probably will not get fully charged, so your figure of 13.8 to 13.9 is pretty close to perfect. Mine sits around 13.7 to 13.8V.
The important thing is that the charge voltage stays fairly stable when the revs rise or when you load the alternator with all the lights.

[james 1992 940]

Thanks narc, I knew somebody would know the specifics.
Off outside now to try your full load test :-)

[Easy Rhino]

Originally Posted by narc

The important thing is that the charge voltage stays fairly stable when . . . when you load the alternator with all the lights.

That's a really good point, narc, and the best early sign of an alternator going south.

The lowest voltage you should see on output would be when hot (as heat increases, resistance increases, and voltage will drop correspondingly), engine idling, with all lights and accessories, including A/C, on. Since this is not (or should not) be the normal operating condition for the vast majority of alternators, it's okay if you voltage output drops below 13.5 or maybe even below 13V under these conditions. If it drops below 12 volts under these conditions, you are discharging the battery. Not good.

[StanC]

I've just picked up this thread - the alternator on my 1996 960 3Ltr has been putting out just around 13.6 volts now for at least a couple of years. At idle with lights, fan, etc running it drops to about 13.58 volts, but with everything switched off and the engine revved to 2000rpm it climbs to about 13.65 volts. This seems to be at the lower end of the 'recommended' scale, but it's not getting any worse, so I presume that it's just the regulator setting.

Does anyone think that I need to do anything about this?

Stan.