Alternator doesn't work unless accelerator is pressed

I just had the alternator replaced, its brand new, but when I turn my car on it doesn't work unless i press on the accelerator.....any ideas????

Loose belt or incorrect belt routing. Your new Alt may have a bad diode, have it tested.

If its an internally regulated alternator, make sure all of the wires are hooked up, otherwise it will require at least 1500 rpms to activate the alternator for the first time after startup.

It may also be a bad rebuild. Rarely are new alternators actually new. They are rebuilt cores which are just as good as new when done properly. Unless your box specified "new" its not new.

In the future, help us out by always posting the year, make, and model. Although it doesn't seem important for every question, the charging system on a 1962 Oldsmobile is radically different than a 2005 Mercedes.

Its a 1987 Nissan 200SX SE V6, and the alternator is remanufactured. I still dont understand why it wont work when i first start up my car, when i press the accelerator then it works, but when I brake, the needle on the voltmeter jumps for some odd reason. Before the original alternator died, it worked fine, it started up when the car did. My Daddy accidentally connected the negative battery terminal first, and thats when this alternator problem first appeared. The original alternator didn't work for months, then all of a sudden, i start up the car, press on the gas, and it works again. I figured if I just replaced it, then it would solve the problem.

if you just bought the alternator doesn't work until you rev the engine, return it and get a new one.