Audio Systems: Car Audio, rca cables, rca outputs

Question
My '93 Nissan has an Alpine FM/AM/CD Player with RCA-type subwoofer outputs. I'm adding a Dual amp and subwoofer, but cannot get any sound out of the subwoofer. The amp has power and is switching on/off with head unit as it should. I've been through the player set-up to insure the subwoofer is set to "on". How can I test further to locate the source of my problem?

Answer
Plug your RCA cables into the full range RCA outputs just to test. If you get sound, switch them back, and set the sub output level higher. The crossover on the amp should be set to full pass thru, or full range, as you are using the crossover in the head unit.