1995 Pontiac Sunfire New battery won't hold a charge.

Hi, was the alternator, checked on or off the vehicle? Did the shop test for a battery drain?

If the problem was the wiring circuit to or from the alternator, that won't show up, testing alternator in store. The alternator itself, may be fine. The charging system needs to be checked on the vehicle.

To check for battery drain, you can check for excessive amp draw, everything turned off. Usually around.030 is normal, no where close to half amp. I don't have the exact spec in front of me. If the drain is excessive, you can pull fuses, one at a time, when you pull the fuse on the affected circuit, the drain will drop to normal. Check for any lites that may stay on, best time to check is in the dark. Ash-tray--glove-box--interior--under the hood-- in the trunk.

An older way to check for battery drain, is to take battery cable loose, use a testlite between end of cable and battery post, if the lite stays on, there is a drain. Then you do the same thing with fuses, one at a time. I think it is best to check amp draw.

With the vehicle running, it should be the alternator carrying the load, not the battery. If something is wrong with the charging system, it will start taking it from the battery. The way your talking, I'd have to check the charging system on the vehicle. If you have a digital multimeter, and want to do testing, I can tell you how to start?

With vehicle and everything turned off, place meter leads across battery posts, take a reading. The generic spec for a fully charged battery is around 12.6 volts. If the battery is run down, take it off and get it charged.

Then start the vehicle, take a second reading across the battery posts, the second reading should be higher than the first, if the charging system is working.

It looks like the alternator isn't charging. Maybe a problem with the wiring circuits to or from the alternator? Do the same test at the alternator bat terminal. Engine off and engine running. Don't get the leads caught in anything. Use a metal part of engine for meter ground. If the second reading, engine running, is higher, there is a problem with the wiring circuit from alternator to battery. If the second reading still isn't higher than the first, you need to check wiring circuit to alternator. I know you said the alternator was good, right?

I'd use a digital multimeter and check voltage at all generator terminals, engine running.

They also call it an alternator. Databases are not always correct. That wiring is what our database showed.

One end, plugs into the alternator. If that isn't factory wiring, I'm not sure how to help? If your talking about, the end of wiring harness, away from alternator, yes it should be plugged in.