I feel like I should know this, but for some reason I don't. The "Switched Ignition" wire that tells your radio the ignition is turned in and allows it to turn on - Is this triggering a relay type thing in the radio and opening a circuit so the radio can be powered by the constant battery wire, or is it actually powering the stereo?

Here's why I ask, and yes it's a stupid idea but I'm going with it anyway :P

If I were to mount a second head unit somewhere else in the vehicle, would the remote turn on power have the required voltage to turn a second head unit on (in addition to the two amps it's already powering) or would I have to run a switched ignition to it from behind the radio, or wire up a relay off the remote turn on lead, or ... whatever else might work. I've already got the remote lead in the trunk and obviously have constant power and grounds via the amp wiring, I couldn't care less about the illumination, speaker leads (there aren't any in this application) or whatever else, I just need to get it powered and prefer to do so with the least amount of wiring to clean up later.

Any thoughts?

 

You can always give it a try, to power both radios from the same power wires. Worst case scenario, you burn out the fuse. If it does fail, don't just put a bigger fuse in though, run your own primary wire from the battery, split it into switched and constant, and have the switched power operated by a 12v relay attached to the original switched power wire.

 

In theory the switched ignition wire is a low current turn on lead just like an amp uses. However, this can change from manufacturer to manufacturer. It is easy enough to test though if the you an ammeter - wire constant and ground, then put your meter in between power and switched ignition input and measure current draw. Anything over 200mA you would be best off to use a relay.

 

fyi theres the ignition swtich wire and a 12volt wire. the ignition wire is like a remote wire but is 12 volts and the 12volt wire (yellow) is wats powering it. remote wires (blue/white) i always thought carried less then 12v, i could be wrong and it is 12vs lol. check with the manufatures if the remote wire needs to be 12vs

 

Every amp I have ever seen has had a 12vdc remote input. Every aftermarket deck I've ever seen has had a 12vdc remote output. Some OEMs do use 5vdc remote turn on leads.

 

To clarify the purpose, I've got a Pioneer Z-120 in the dash but it's DSP control is basically non-existent and I'm not happy with the passive crossovers on my Focals up front. I'll run the RCAs out of the Z-120 into the AUX IN on my old DEX-P9/DEQ-P9 and use them for tuning, but they'll be trunk mounted and forgotten about once tuning is done, all control will remain through the in dash Z-120. I was just trying to be lazy with how I was going to wire it to turn on, in the end a relay makes the most sense, I'll do it right the one time so I don't have to mess with it later.

Thanks for all the responses folks, much appreciated.

Edit: (Constant) Power and Ground are still coming directly from the battery and being tapped at the fused distribution block/ground distribution block already in the trunk for the amps, it was just a matter of how best to get a remote/switched/relay turn on.

 

iirc its ok to "daisy chain" a remote wire. ive done it before