I have a problem with my sub woofer in my car. It use to work fine, but now it pops in and out whenever it wants to. Do I need to buy a new sub woofer or could there be just a loose connection? Thanks.
Your issue sounds to me like a loose connection. I would recommend having your power, ground, and RCA wires checked to make sure they are connected properly and that no loose connectors exist.
If the subwoofer itself were faulty it would not work at all in most cases. It is also possible that the amplifier could be overheating somehow, causing it to go into fail-safe mode to prevent a fire. When the amplifier cools back down the subwoofer will usually turn back on.
If you need assistance with these checks, feel free to contact a certified mechanic who can ensure that your electrical connections are sufficient in order to get your subwoofers working again.