Alternator Multimeter reading

[Tom1]

I'm getting a reading 12.09 volts with lights and blower on on a stock 45amp alternator at idling speed. Is it normal to be that low while idling? The volts increase to high 13's as speed increases.

[pkbinplano]

sounds about right

[Tom1]

That's good, thanks. I just got a new alternator and wanted to make it sure it's working properly.

[02for2]

Actually, that sounds a little low to me. The Bosch alternator should put out between 13.5-14.5VDC @ 1k rpm if battery and alternator are healthy.

The battery alone should produce about 2.2VDC/cell or about 13.2VDC w/o load - I would test this as you may have a bad cell or some sulphating of the plates - how old is the battery? 12.9VDC is definitely on the low side, but as long as you're above 11VDC, all the diodes s/b working.

Cheers!

[TobyB]

at idle with lights and fan, I could see it not charging-

when you rev to 1500, does it hop right up?

t