one channel on amp not working

I have a 2 channel sub amp, the right side does not work the left side does.  If I switch the red and white on the rca right side does work the left does not.  Would this be a problem with the amp or the cable?  I do have  a meter, is there a way to test the cord or amp using my meter?  thanks in advance for any input.

The problem is NOT the amp. Do the same test at the stereo"s output. If you get the same results, The RCAs are faulty. If there is no change, the problem is at the headunit. If u want to use the multimeter, you'll need to test the output of the unit on each of the RCAs of the stereo. Set the meter to AC voltage, set to PEAK HOLD. and run a test tone or simply play a song at approx mid level output. Depending on your brand of stereo the voltage should read about 2V. easiest way is the first one i mentioned.