Can I hook up subwoofers without installing them?

If the buyer has a pre-existing setup, then hook it up to their vehicle. Otherwise you will have to run speaker/ground wire from your stereo and battery.

Assuming you have an amp in your car and the subs are boxed then yes, just switch over the speaker wires and play music through your head unit. You wont be able to if the subs aren't boxed and there is no amp present.

you would have to run it to some speaker wire from your car. you can run the power and ground from underneath the hood to test the amp but you need a radio hooked up to it to get sound

After interpreting what you wrote, your tries to restoration it, i could recommend procuring a noise filter out. now and lower back the cables linked to the amp %. up engine noise. I had that happen to my device as quickly as yet i by no skill have been given a noise filter out by way of fact i bought the automobile. the two its that, or i could say its the amp. attempt hooking up yet another amp, if it does the comparable element, then you definately choose a noise filter out.