From how i understand you statement, and your subs are connected in a bridged fashion, then i advise a word of caution, as i believe that you may be imposing a serious load on your amplifier. the sub that is not playing may in fact be shorted and that is why it cuts the signal to the other sub. the amplifier sees both subs and the shorted one will impose a serious load and can cause the amplifier to fail if driven hard. separate the subs and meter them with an ohm-meter and see if they are close to the same. if they are 4 ohm for example, they might read around 3.2 ohms, etc. using a dc ohm-meter is not an accurate to measure the impedance of the sub, but it is accurate forcomparing two subs. you will probably find that the one that is out is shorted and will read below one ohm. everything that i have stated so for, takes into account that your subs are bridged to the amplifier. if in fact they are not bridged and on separate channels, then swap the subs around and if the bad one starts playing, then you have a bad channel on the amplifier or a bad input to the amp lifer. at this point you would swap the rca inputs around and if the bad sub that started playing when you swapped it around, goes out again, then it is an input problem which then you should check the rca cable or radio itself. i know my statement may be a little confusing, but if you follow them exactly, you should be able to determine exactly what is at fault. let me know if you need further assistance....v
Answers & Comments
From how i understand you statement, and your subs are connected in a bridged fashion, then i advise a word of caution, as i believe that you may be imposing a serious load on your amplifier. the sub that is not playing may in fact be shorted and that is why it cuts the signal to the other sub. the amplifier sees both subs and the shorted one will impose a serious load and can cause the amplifier to fail if driven hard. separate the subs and meter them with an ohm-meter and see if they are close to the same. if they are 4 ohm for example, they might read around 3.2 ohms, etc. using a dc ohm-meter is not an accurate to measure the impedance of the sub, but it is accurate for comparing two subs. you will probably find that the one that is out is shorted and will read below one ohm. everything that i have stated so for, takes into account that your subs are bridged to the amplifier. if in fact they are not bridged and on separate channels, then swap the subs around and if the bad one starts playing, then you have a bad channel on the amplifier or a bad input to the amp lifer. at this point you would swap the rca inputs around and if the bad sub that started playing when you swapped it around, goes out again, then it is an input problem which then you should check the rca cable or radio itself. i know my statement may be a little confusing, but if you follow them exactly, you should be able to determine exactly what is at fault. let me know if you need further assistance....v