Im running a continuity test on my system. When swtich is off, the multimeter read high resistance of about 75 ohms but no buzz, when switch is on, the tester buzzes and the resistance drops to 11-13 ohms. Why is it doing that? or is there something wrong with the system?

 

You cannot run a continuity test on a powered system.
The power can interfere with the measurement an cause a false reading.

Continuity is measured by applying a small DC signal to the circuit and measuring the result.
Obviously any other current or voltage in the system being measuring will cause that measurement to be in error.

 

What reading do you get if you touch the multimeter leads together?