Acoustic Research HD510 defective sub?

I purchased a set of HD510 speakers and they were delivered yesterday. This is the best speaker set I've ever owned so I hooked it up to try it out. I thought it sounded great but after a while noticed there was no sound coming from the sub. I went to check the connections and noticed the power light had changed from green to red. I pulled out both the L/R rca connectors and flipped the power switch off and on. The light stayed red. As soon as I touched one of the rca connectors to one of the inputs, the light turned green and the sub was working again. It would work for a while but then cut off again. I thought maybe I had it connected wrong. I waited until this morning to try it without being connected to anything. After about 30 minutes of being on, I heard a faint click and the power light changed to red. This was without being connected to anything. It's obvious it's going to keep doing this so I'm wondering if it's defective and has to go back or is there anything I can try? I don't even own a car, so if it has to go back I'm going to have to hope I can schedule a ups pickup or take a cab to Best Buy to return it. I also have to hope I can return an online purchase in-store. I'd prefer to keep this set because it will only cost $135 after Bing cashback and I can't afford much more. TIA for any help.