I bought the car used. The rear speakers weren't working when I bought it. I assumed they just needed to be replaced, and as I intended to upgrade the factory HU (single CD player w/weather band radio) and all speakers anyway, I didn't give it much thought. I did some exploring, and found that the front speakers had been replaced with decent Pioneers by the original owner, so decided to install new rears only. Last week, I installed my new HU and speakers, but no luck. The rear speakers still aren't working. Can anyone advise me on how and where to look for issues? I own a multimeter.