how to know car alternator is having problem

What sort of voltage are you seeing across the battery when the engine is idling, with minimal electrical load (ie. no headlights, fans, demister, etc.).

If somewhere around 14volts you are probably ok. If much higher, then the regulator/diode pack on the alternator might have failed. If the battery voltage remains the same (around 12) or even drops when the engine is running then something isn't right (alternator, cable, crimp, fuse, etc.)

Looking at your other post, you need to sort out the melted fuse box/bad alternator cable. The alternator is working and providing current otherwise the the fusebox wouldn't have melted.

Looking at your other post, you need to sort out the melted fuse box/bad alternator cable. The alternator is working and providing current otherwise the the fusebox wouldn't have melted.

i went to a local mechanic so he connected the black wire from alternator directly to the battery and he said it wont create any more problem. It seems to be ok so far. has any one done same thing? and did it create any sort of problem

Thanks,

Joseph