If you haven't done it already, you'll want to give the battery a good charge from a battery charger. Cables disconnected of course.
I too thought that the belt might be slipping, but I checked mine with a Krikit at install and post install.
What is very interesting is that if I don't go above 2000ish rpm, the alternator won't light off. Time does not appear to be a factor. We confirmed this one winter morning (-5 degrees in MO) when I thought I had throttled up for light off but hadn't. When I returned to the car after about 10-15 mintues it was trying to die and I noted the voltage was still holding at 12. I revved up and it fired off. Started purring like it had a fresh sauscer of milk.
By the way, in my case, the alternator case is nothing like the Bosch/OEM case. Voltage regulator on the back of the alternator was not Bosch either.
It works, It was cheap, but I'd probably not do it again. OEM to manufacturer's spec almost always wins out. But I do have to re-learn that one every once in a while.
S, J.R. Brown
2000 G500 LWB Obsedian Black
2005 Toyota Tacoma Access Cab Off Road Sport
1993 Volvo 240 Sedan Anthracite
1980 450SEL Champange (owned it for 15 years. Great car)
1986 280GE LWB Anthracite (Sold it and kinda wish I hadn't)