Alternator Replacement, 95 Lumina, 3.1. ?

I have a 1995 Chev Lumina, 3.1L, 112K miles. My question is how do I know when to replace the alternator before it actually dies. Had it checked at Auto Zone while it was sill in the car. It read 14.2V, 45A at the battery terminals. 45A seems low. any opinions....thanks.

I'm sure they used a little handheld "battery tester"? If so they are not the most accurate. We have the latest and greatest, we can check the same car 3 times in a row and get three different reports!

Personally I would wait for the old one to fail. You might as well get your moneys worth. If you go with a lesser quality replacement alternator it could give you more trouble than the one you have now. Its an easy enough alternator to replace, you can find them at virtually any place that sells automotive parts, and there not that terribly expensive. When it does fail your only looking at about an hour out of your day to replace it.

Airjer_ Thanks for your comments. Yes, they used a hand held one. It's not the hour or so to replace rather than where it fails. The alternator failed on my wife's 2000 Ford Windstar (65K miles) last month in down town Raleigh. I had to get it towed to my house and replace with a brand new unit (not a refurb) next day. My son uses this car at his college about 25 miles from here. Don't want to get a call some day to rush up there.
The belt was showing some cracks so I just changed it. Could have changed the alternator as well which probably would last the life of the car knowing this one lasted 15yrs already. May be will do it next spring unless it is needed earlier...........thanks for your advice any way.

as far as I remember there should be a warning light on the dashboard
if the alternator fails.
I wouldn't trouble trouble if there's no sign of an undercharged battery.
By the way, is the belt tight? Proper belt tension is essential for alternator.

I changed the battery about a year back. I think it was the second one in 13 yrs. There is no sign of not charging and yes, the belt tension feels good and tight. I think I am going to wait until I see some symptoms of failure. I had a 95 Lumina 3.4L also. The Alternator went at 50K miles and then another about 50K. My Ford Windstar Alt went out at 65K miles. That is what prompted me to ask about this..If and when needed, I am going to do it myself. Refurb one is about $129. Brand new one $169.