Drive belt question

[kxl77]

So I replaced my alternator belt, but I realized that I placed the belt over the idler pully. Now I realized that when I tried to jump a truck today, my car died. And when I had the heat on blast with everything running, my lights would dim a bit, and then go back to normal after I increased the RPM's.

Would this be the reason why my lights are dim or should I replace the alternator...

[Tim95M3]

haha dont jump any trucks :nono
The lights dimming is somewhat normal. I would put the belt BELOW the idler pulley though cuz thats where it belongs.. belt is looser being above it, therefore may slip