Ok im going to try everything today in a bit. Which fuses should I check?
Also, do I check the volts on the alternator which the car is boosted with the cables on or off? Because if the cables come off then I have to rev it for it to stay on. As soon as I stop reving it starts to die.

 

take the alternator off and take it down to any autozone or advance auto part store.
they can test it for you(its free). have you check the connections on the back of it?

 

which connections in the back?
and I dont think we have those stores in Canada.

 

in the back of the alternator. ah canada that explains why there isnt any of those stores cause canada dont exist... get a volt meter and get a reading of the output of the alternator,

 

How should I take the reading though? While I boost the car and leave the cables on? Or take the cables off and rev it and get someone to take the reading? Because it will just die if I dont rev it and the cables arent on.

 

If your battery can't keep the car running, it is bad or run down. A car with a bad alternator but still some charge in the battery should idle OK.

Parts stores that have a consumer focus (advertise to the public in newspapers, etc.) usually offer testing of alternators and batteries.

 

Well the thing is that, If I put a new battery into it, the battery will slowly start dieing like how it did before. I put my friends battery in it and it started then we used to volt meter and checked the battery and it was going down pretty quick.

 

Right, showing that you aren't getting any charging from the alternator. But you can run off of a charged battery for a few minutes for testing, without having to rev up the engine.

The big wire on the back of the alternator should have battery voltage to ground all the time. The small wire on the "I" terminal in the 3 or 4 pin plug should have battery voltage with the key on (engine need not be running). With the key on and the engine not running, the battery light on the dash should come on. Do all these tests check out?

 

Ok I found out the alternator is working fine. So what could be the problem? The connection wires?

 

triple check all the plugs on back of the alternator, the fuses(under hood and dash)
make sure your motor is grounded to the frame or to battery.
also test the white wire the goes to the fuse box under hood that is the recharge from the alternator that goes to the battery.