Auto Repair Q&A



Cooling System










Auto Repair Products

Stereo and Speaker Wiring Basics


Wiring stereos can be tricky, especially when extra components that the stereo itself or sound system setup may not be specifically made for. Adding subwoofers, for example, can be problematic even when all of the right components are included to make it work correctly. This is what user bobepainter in our forums found out when tricking out his Grand Marquis with new beats.

The long and the short of it is that while he had the correct extra components to boost and regulate the added subwoofer, Bob did not wire their power sourcing correctly. This can result in several things: blown fuses, battery siphoning, or just a constant power drain when the vehicle is running like Bob experienced.

The answer? Simply put, if the item is being added to the stereo, it should be on the same circuit (power input) as the stereo using the same relay that activates other sound system components when the stereo is in use.

In other words, the circuit to power the stereo itself should have a relay after the radio's power switch that sends juice to other sound system components when the stereo is on and that stops sending that power when the stereo is off.

That relay may be easy to find or it may be highly confusing, depending on how customized your sound system is. On most stereos, that power relay will be in the passenger's compartment fuse box itself, usually right next to the stereo input power fuse. On others, it could be on the back of the stereo, at a junction somewhere inside the dashboard, or even in line with other stereo components nearest the radio itself. Depending on how the system was set up and by whom.

Most quality installations will use a spare fuse space in the fuse box for this relay. Others might have it conveniently located under the stereo is a space in the dash that is easily accessed with a single panel removal or the opening of a dash component (such as an ash tray or phone holder). Shoddy installations will have it hidden in a cluster of items deep inside the dash or on the back of the stereo itself, requiring its removal to add components.

Just remember that if the switched voltage input is not set up correctly, your stereo system will have components that either don't work at all or are always on, potentially giving off unwanted sound or using battery power when you don't want them to.