THIS WILL ONLY WORK IF YOU HAVE AN EXTERNAL AMP!
It will also only play through the speakers connected to your amp.
This is a very simple solution to a problem many people have. To accomodate both my iPod and HU I have built a switch box to control the source. It's very simple! All you need is a handful of parts, a soldering iron and a DMM.
(Do this at your own risk...if something goes wrong you may damage your amp, iPod or HU)
Step 1: Parts and Tools
6x RC sockets
1x 4 pole switch
A small box to house it in
Some good quality wire
A Multimeter (to check continuity)
Step 2: Wiring
To do this put the switch in a know position and pick a start point.
Using your multimeter check the continuity between each contact and note which ones are connected.
Do this for all the switch positions and you'll soon be able to see which contacts are the main connectors.
Now the key is to be consistent. Start with all the right audio plugs.
Connect the main contacts to the amp plug first. Then connect the other two contacts (for the two positions) to the HU and iPod plugs. MAKE SURE YOU ARE CONSISTANT WITH YOU GND AND POSSITIVE LINES!
Repeat this for the left audio plugs.
It's as simple as that! Make some nice labels and mount it in your car somewhere accessible.
and thanks for reading my first instructable!