Discharge on electrical system.

[alpinaguy]

Just installed a New 318 80 amp alternator last week and it's fine when nothing is on. Charges at just beyond 13.5 volts but when I turn on lights or even hit brakes there is a drop in the system. If everything is on it all goes below the 12 volt mark. Took the vehicle in to the alternator shop and had alt tested and was told nothing is wrong with the unit. Any thoughts? Did I not hook something up correctly or leave something unfinished? TIA. AG

[c.d.iesel]

look to bad ground circuits, lack of proper ground wires

from motor to body

battery to body

alternator to motor

what / why was the alternator replaced to begin with?

maybe the same problem exists ? ? ?

[alpinaguy]

Thanks I'll try all those. i had also moved battery to back w/strut tower brace maybe the battery ground is the issue. When I leave it hooked up after two days my new battery is dead too. Hope this is all tied together. Thanks for the input. AG

[c.d.iesel]

new battery dead after a few days could

also be caused by bad diodes

in thet 'new' old rebuilt (not) alternator ?

[SteveJ]

Disconnect the battery ground, clip on an ammeter in circuit and see if there is a draw with everything turned OFF. For our old cars, the only thing that should be drawing any amperage (with ignition off) would be the tii clock(if a tii), and maybe a stereo memory circuit (if such a stereo is installed).

If you see any current draw, then start unplugging items while watching the meter. I would probably start with popping out the fuses one by one.

[BillWilliams]

Does the light on the dash behind the "L" light? It is part of the charging circuit