Does this sound like a faulty alternator?

[astat1]

My battery is new and holds a charge well (13V). When my car is cool and running the alternator is charging battery (14.6V across battery terminals). When the car gets hot the voltage across the battery shows 12.5V and my amps gauge is in the negative. Could it be a bad voltage regulator? Thanks

[Nacho-RT74]

is that at iddle ?

[astat1]

Yes.

[Nacho-RT74]

so you get 14.6 warming engine and riding ?

Mopars doesn't charge at iddle unless gets 1000 RPMs or so, or upgrade on alt ( kit, smaller pulley, newer alt... )

[astat1]

Thanks Nacho, my problem seems to occur when the car gets to normal operating temp (180 F). Then I get the 12.5 across the battery and a negative reading on amps gauge in dash.

[71_deputy]

couple of things to check.

make sure engine grounds, alt.housing is clean- not rusty or dirty so it can't ground to the engine block.
check bulkhead connectors- tight and clean, voltage reg.- good ground behind it.

I always add another ground strap from the back of the left head to the same bolt as the voltage reg.- this will help in providing a proper referenace ground for the reg.

check the terminals on the alt- could be loose enough that when it gets warm there is too much resistance.

alt could be breaking down inside when it warms up.

John Mac

P.S- Natcho- we should put a post up to allow others to check thru with this info!!!!!!!