Bad alternator?

My lights have been going dim for a few months now at night occasionally. I figured my alternator was going bad.

Last Sunday my van wouldn't start and we couldn't jump it. We bought a new battery and it started just fine and has all week.

Parked it yesterday morning at 7am, went out at 1pm today and nothing. No inside lights or anything. Jumped it and it ran fine until I turned it off. Same thing.

Jumped it again and went to AutoZone, they say alternator is bad.

Searching on this site I found the service bulletin saying that lights going dim were because of a screw on the voltage regulator.

Could this also be the cause of the other problem?

I cringe at the thought of how much it is going to cost to replace the alternator. I know the part alone is $150, but labor is going to be a killer as everything I read said the engine would have to be rotated and framed dropped.

I removed and repaired my alternator twice easily on my '93 3.8 but hard to reply for yours (about access) as we have no indication or model year, engine type...
Lights that go dim as the car is running is a definite indication of loss of alternator performance, so battery was probably good and failed jump start was due to poor connection with jumpers. Jump start is best performed by letting the other car running for 5 minutes to accumulate sufficient charge in the failed car battery. Jumpers smaller than 4 gauge are improper for direct starting from other car battery.

Sorry, I had put that in the subject and then changed it.

It is a 1998, 3.4L engine.

I really think the past battery was bad. I was at WalMart and they brought the portable jumper and then my husband came with his truck and tried. We used the same jumper cables to jump it yesterday and they worked fine.

We left them on for about 20 minutes and it still wouldn't start that day until we got a new battery.

Update--

Had the alternator replaced on Wednesday. Haven't had a problem since. Until.....today at Walmart.

Came out, turned key over and all lights came on like normal. Then they immediately went off and it was COMPLETELY dead.

Jumped it with cables, after letting it charge for about 5-10 minutes and it started right up.

I didn't try starting it after shutting it off again when we got home, but the lights came on when we opened the doors to unload it.

I'm puzzled. Has new battery and new alternator.

THere have been several reported cases of corroded contacts, specially the one on the starter post. Check them all again..including the battery. At one time, I woujld have sworn my cables to the battery were neat and clean..just to discover after hickups and mind boggling investigation that the connector end to the battery had a black hard coat of oxyde . Scraped it off and all went back to normal.

I think LMP hit the nail on the head. Battery terminals can look clean but if there is that hard black coating on them they won't conduct electricity very well.