How can you tell if the BAC is bad?
 

'91 N/A

FSM says that key on and idle should be approx. 8.0 V. Engine cold key on, mine registers 9.6. Fully warmed up at idle and its increased to 10.8V.

I took it off and cleaned it well. I applied 12V and ground to the terminal and it worked fine. Put it back on and the voltage readings didn't change. Is it bad and needs to be replaced?

Check this out... http://www.teamfc3s.org/info/articles/idle.html