check head unit amps etc?

Just lost the left side sound in my system (Alpine CDA-7873 and MTX Thunder 4300x) My first thought was that the amp was the problem, so I yanked it out thinking to put another amp in. Then I remembered that I had had a similar problem which led to the head unit repaired 2 yrs ago. They replaced the internal amps. I did not think to switch the rca wires around to see if it was an amp or head unit problem. Its hot and I am lazy and dont want to hook it back up to check. Can I use a volt/ohm meeter to see if there is a signal down the rca channels. If it is possible what would be the best way to do it.ThanksBRM+MGM+JRM2+SAM Forever!!!

"The ability to reason drives us relentlessly to find the truth." A. Einstein I think????

Set your meter to the lowest AC Volts setting. Turn the radio up as loud as you feel safe with your speakers. Touch and hold one meter lead to the shield of the RCA cable, hold the other meter lead to the center conductor of the same cable. Do this with both the left and the right RCA cables. The voltages should be similar between the 2 channels if your radio and RCA cable are in working order.