Amplifier stops working at higher volumes - not clipping

[Nu2droid]

Ok, a second volt meter show .2 AC at the inputs. And 5 at the outputs.

 

[Nu2droid]

Question. ....

What happens when you draw more ohms then allowed.. what I mean is if the radio channels are 4 ohm and I am adding the 4 ohm woofers to the existing car speakers... what will happen? Would it cause this?

The description of the amp says ,"Input sensitivity: 200mV-5V". So the .2 volts I show at the input is good. Correct?