No Power?
 

For some reason out of no where, my bonneville when jumped runs, but when you turn it off and try to turn it back on it has absolutely no power. I think it might either be the battery or the starter.

i would check for corroded terminals and get the battery tested first... a starter would usually give you troubles even when jumped,

If jumping it works..then it's not the starter.

Battery or alternator. If the battery is bad..it won't hold a charge. If the alternator is bad..it won't charge the battery. Most likely it's a bad battery.

I changed the alternator and it seems to be running fine. I also bought a new Voltage Regulator, but I have no idea where it goes. Can anyone help me? It goes with a 78' pontiac bonneville, 350 chevy

Does it have an external regulator? Many times it would be an integral part of the alternator. If it does have an external regulator, they were generally located along side the radiator on the driver's side of the vehicle.

If it looks like this one then it goes inside the alternator. Take it back & get a refund.

http://www.partsamerica.com/product_.../sta/vr111.jpg

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