The options would be for the amp on wire to go toeither a toggle switch, hooked to a wire that gets power when the ignition is turned on, or a relay. The relay is my own preference, and is the most "professional" (whatever that may mean) approach. The toggle is the dead easiest method, the biggest shortfall is that one is bound to leave it switched on sometime, and might come back to a dead battery. I know of that happening at least four times to folks who use the approach. The middle of the road approach is Dale's, hooking into a wire in the car. It is not as hard as one might imagine, do you have a continuity test lamp? If not, get one! They are a cheap item that is useful in most any electricial diagnosis process in either a car or house.
They most often look like a pointy screw driver with a wire terminated on a clip coming out of one end. They are easy to use. You hook the clip to a ground surface, which in a car is the any metal of the chassis or bolts screwed into the frame. Then you touch (gently) the point of the screwdriver end to a bare wire. If there is a postive current, then a lightbulb in the handle will light up. Simple eh?
Look in the fuse panel for a switched fuse. All that means is when the ingniton is turned off and key out, there is no power to the fuse. Then turn the ignition on, and see if you there is power, if so, you have found a love match!!
Radio Shack sell a little device for car fuse blocks called a fuse tap. Get one and use it to on the fuse you have found to wire off of, wire the amp into it, and you wll be done.
This is just one method, but it should work. If not, come back to the board and just ask for help! There are a lot of us audio wannbes here that will be happy to try to help you out from afar....
Good luck and tell us how it goes...

 

Thanks for the help everybody, looks like I'll be making a trip to Radioshack tomorrow for the relay. I'd read about it in another thread, that does sound better than the switch.

Again, thanks. My field is molecular biology, very little experience in electronics.

 

Let us know your experence of the relay, it is a neat solution! Glad to see you giving it a try.

 

They also sell those testers at walmart, like $5 or something they are awfully handy

 

I have a 2002 ES and I did exactly what you are doing. I used a wiring harness and a reverse wiring harness to hook up my amp to the stock HU. You said the red wire on your harnesses are 12V ignition/switched. I just hooked my amps remote turn on lead to this wire. When you turn the HU on it will turn the amp on, when you turn the HU off it will turn the amp off. However, when I turn my HU on it makes a very quiet pop noise. And when I turn it off I get a weird noise and I was told it is because the amp is turning on/off right after the HU. I was thinking of getting one of those relay things so that it wouldn't make the noise.

Also, what brand harnesses are you using. I used the scosche harnesses and they don't have a dimmer or illumination wire. Which means that the HU won't dim with the cluster lights and that the buttons on the HU won't be lit up when the lights are on. I don't really care about the dimming but the buttons not being illuminated is annoying. I am either going to try a different brand of harnesses or just cut the stock wires eventhough I really don't want to.

 

Actually the hot wire from to the harness is switched at the ignition, which means that once you turn the key, there is power in that wire, even if you elect not to use it! So the amp is still powered up via the key, and turned off when the key is removed. Your friend did tell you right the thump you hear is based on the sequence of turn on, that is why some amps and some head units have selectable delays for the headunit to come on first, then the amp. I would suspect the sound you hear on turning the headunit off is a similar issue.
While I am like you, having a dislike of cutting perfectly good wires, that is one solution. Another might be to pin out in one of the "extra" pins a set for the radio dimmer control on the radio side, and then wire on your own from the dash side of the harness to a line that dims in the dash. I have not played with mine in sometime, I have a newer mazdaspeed right now and have yet to start tearing the radio out, but I recall there is some weirdness in the dimmer switch itself, perhaps reversed wiring?
Start a thread of your own on your question and you might be a touch more feedback from folks here who have solved the very issues you are dealing with!
Good luck and let everyone know how you solve the wiring.

 

Opus - looks like you have the amp turn on under control.

Dermen/Dave - the dimmer is NOT populated in the Scosche harness (don't ask me why, I think that was a dumb move). Anyway, there is some weirdness to the dimmer - it uses two wires to complete the connection, and the way it operates (if I can remember this correctly) is that there is voltage on BOTH of the wires, one is variable and the other is fixed. As the voltage on the variable one changes, the light of the deck changes. What I did was take some fairly thin gauge solid core wire, strip it to fit the connectors reasonably well, slipped the harnesses in (need to be very careful as the wires are fairly thin), and tie wrapped the wires that I added to the harness to provide some strain relief and keep the wires pushed into the connectors. You kind of have to go this route as you have to plug directly into the deck, there is no wire coming out of the deck that you can splice into.

**edit** I wasn't able to find the pins that the harnesses use in my sources. I could probably have found them, but they would likely be special order so you'd want to be 100% sure of which kind you needed! **end edit**

I suppose you could take the deck apart and solder onto the required spots, but I elected to not do anything so extreme.

So, I do have dimming on my factory deck w/ outboard amp. I took a couple of not very useful photos, I can post them if you like.

Dale.

 

Actually, I'm still working on the damn thing. Havent had too much time with the rain lately. I've checked everything with my volt meter. 12v going down the power cable. Continuity from the ground to the chassis. Radio will operate when I connect the two harnesses, but the amp still wont come on.

I'm planning to run a wire directly from the battery to the turn on before I chock this up to a dead amp.

I'm VERY glad I did this harness/reverse harness method so I can unplug it and run unamplified.