Since you already tried the old trick I would say the alt is gone. Alih is right... never try this 'old shcool' trick on new school cars. The alt has diodes in it, one of those could be cooked, it would not be bad enough to register any 'flags' but just enough for the car to die. Like Alih said, have it tested... and since you are pulling the alt I would test the battery as well. Do you have a volt meter?
Also, what more info do you have? year, motor, etc... Does the car die only after sitting for 20 minutes? why does it sit for 20 minutes? do you drive it? there might be something else wrong as well.

 

Well....that would make it a real ***** to start the engine without a battery.
The engine can and should run on just the alternator. Alternator output is usually close to 14v, plenty to run a 12v ignition. The purpose of the battery, in addition to starting the engine, is to have a "regulated" output of power. But, I don't know about the "spike" issue you mention. You could be correct, but I don't know that doing it momentarily will hurt it? The "remove the positive battery cable" trick is an old one that we gear-heads would use regularly. But it wasn't a big deal with non-computered ignitions. You could remove the positive cable, and the engine would continue running as long as the alternator is good.
Keep in mind though, that older cars didn't have much more than one cable/wire on the positive post of the battery. Newer cars have more than just the one cable. So, if 9camaro5 removed the positive cable, and separated the other "hot" accessory wires from the cable, that could also explain why the engine quit. If all of the positive cables and wires are connected, and the engine kills, then I would say "bad alternator".

 

Correctamundo.........the old cars from the '60's & early '70's you could do this with no worries,even the alternator had a separate mechanical voltage regulator so it was pretty hard to hurt anything,hell I've swapped batteries in cars of that era and had them sitting there running with no battery in them at all let alone just one cable pulled.
They run fine off just the alt but you've got to have a battery to start'em.
I quit using this trick when GM went to the "one wire" alternator with built in regulation because you can damage the diodes in the alternator,so I've been told anyway.
I've seen it done with no damage but it could happen I guess.

 

ok got a brand new alternator in, i hear rubbing, the belt is clean and new as well, pulleys and tensioner are clear of dust etc...
small(barely visible)puff of smoke comes from area of power steering fluid resevoirand i can smell rubber, i have no idea where to go from here and am lost, anybody know of any camaro guys in langley b.c. nice enough to help out a stranger?

 

i think we need moreinput jonny number 5

 

[:@] come on kids the backyard terminal removal can help diagnose charging/ battery problems and usually wont do much damage in the older cars but anything with electronics really squeals and does not like this method. spend a couple bucks and get a volt ohm meter. this will be handy for many years to come and not just for this job and remember you get what you pay for, you buy crap from the local cheap chain store then dont act surprised when stuff dont work!. anyway the volt setting on the meter can diagnose this problem. obviously the battery cant be in good shape if the car only runs for twenty minutes on a full charge. batteries can be bad right out of the box, ive seen lots especially exide brands and those from the corner discount chain( interstate is my recommendation) they can also show twelve volts but have no amperage available and no reserve capacity. if this is all your battery is capable of then it needs to be charged properly (overnight 1-2 amp trickle) and then properly tested. lets get this done so we know we have a good foundation and well go from there. remember these cars have several fusible links and these should be checked also, if you dont know what to look for get back to us kurt