Isolators are only necessary if you play your system for long periods without the engine running/alternator charging the batteries. The isolator is wired into the ignition feed and is essentially a large solenoid that just disconnects the audio battery from the rest of the system when the key is not in the "run" position. This allows you to use your stereo (or whatever you have hooked up) as long as you want and even if you run the battery dead, once you turn the key on, it will tie that battery back to the regular charging system and main battery allowing the car to still start-and let the charging system recharge that drained battery again also.

We sell the PAC disconnect solenoid. We have had ZERO failures with this unit over the years. There are some cheaper versions out there but the point of having it is to keep from getting stranded. Why even bother installing it if you are going to use something that may fail?

Anyway, they are not as popular as they used to be. We end up using them more on our marine installs than anything. We use a few for the tailgating nuts and some of the highschoolers but other than that.

Below is the link to PAC's .pdf instruction manual on it. Maybe that will clear up some misconceptions about isolators...

http://www.pac-audio.com/PACProductD...ons_072006.pdf