Using A Relay

[plazman 10+ year member]

the 12v power gets fused correct?

 

[Slody4Futbol 10+ year member]

yes yes

10chars...

 

[helotaxi 5,000+ posts]

since when? ive never heard about using relays on a remote wire =\
30 amps? jesus. shouldnt that be much less? its basically a non-breakable fuse- it just switches to off like when you 'blow a fuse' in your home.

use it if you want. its only $2 + s&h. or just get a really low rated fuse.

It is pretty obvious that you have no idea what a relay is. A relay is a switch. It uses a low current (or voltage) "signal" to switch a higher current (or voltage) source. The reason you want one on the remote lead when you are wanting to switch multiple components is that the remote out on the HU can only muster a very small amount of current before either the voltage drops below the switching threshold of the components downstream and they don't turn on or the output of the HU cooks itself. By using a relay, you can switch a nearly unlimited number of components and only place the demand on the HU output of the relay.

The 30A Bosch relay is overkill, but it is the standard automotive relay and is cheap and easy to find a replacement if it goes bad (I've had one go bad though it is pretty rare.)