1997 GMC Sierra 4x4 voltage issue

[Chevy's Rule]

I have changed the alternator as the front bearing was making noise. Now it seems like it may be eating the belt. But when i turn the blower motor on under low rpm's the voltage drops to 9.5-10 volts and stays there. if i turn the blower motor back off a few seconds later under high rpm's the volts jump back up to 14. Any ideas?

 

[Grolla42]

How are all the connections? no corrosion or wear?

 

[Chevy's Rule]

No everything good. Somebody mentioned possible regulator/resistor for blower motor. Don't know though. Looking for any ideas.