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nissan
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Discussion Starter · #1 ·
I think my alternator may be wearing(worn) out.

I've noticed recently that at idle the volt guage only reads 12v, as soon as you pick the revs up above 1200rpm it reads just above 14v.

I have double checked the above readings with a digital multimeter.

i have duel 86ah batteries fitted and the alternator is only 70amp, could it be that the alternator just carn't keep up?


It's a 1994 td42 wagon
 

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Mate, I'm no auto electrician, but those readings sound normal to me. At least, I hope they are, cause mine reads the same as yours! You'll probably find that at idle the alternator charging hasn't kicked in so the 12v reading is what your batteries are at. When the revs pick up the charging circuit kicks in (dunno the technical reasoning behind it, I just know you need revs to do it) and then the normal output of the alternator is shown - pretty sure 13.8 - 14.4v is normal. If the voltmeter shows less than that at 1000 rpm then it's not charging at all, and if it's more than 14.4v then you'll probably end up boiling the battery.

anyway, that's my understanding of it. Glad to be corrected by an expert :)
 

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GQ Dual Cab. TD42Ti with fruit.
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Service manual states to test at 2000rpm, at which point you should have between 14.5 & 15V.
 
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