I am having issues with an amp, and cant find the problem spot. My first question is, should my RCA/phono jacks be giving a reading on a multi? Even spiking, etc...? From my knowledge, they should be, but Im not a car audio expert.

Thanks!

 

they carry ac, so you switch your multimeter to AC volts (vac). It is a low level signal that should only be present when you head unit/ processor is playing music. What you see on your meter is determined by what 'volume' your source is as well as its possible output like 4v preouts, 2v preouts, 8v, etc. (these are normally the max values)