I just got a Kenwood HU for my car yesterday and was wondering if hooking up the Illumination wires will do anything? I read somewhere that the deck wont dim even if you hook it up and try to adjust it to dim with the rest of the lights. Can someone shed some light on this please.

If you hook that wire up to your car's + illumination wire (usually orange or orange/white on an aftermarket harness) the deck will dim when the headlights are turned on. The level of dimming is not adjustable with the dash lights or anything like that.

just to let you know, DO NOT make the mistake of attaching the illumination wires with the dimmer wires from the headunit to harness. this WILL short out your dash lights. it happened to me, and i'm just trying to save you a headache.

lol yea just remove the dimmer wire from the harness so nothing bad happens. you can use the illum wire just to have the deck dim with dash lights. i think its a useless feature, i like mine to be bright at night but maybe some decks would be too bright.

Ok, Im going to remove those all from the harness

So I've been debunking this myth for a few years now and I don't want to get into a big thing but here's the deal. If you hook the illumination wires up incorrectly it can cause damage or problems to that circuit. Of course, if you hook up any circuit incorrectly it is very likely going to cause damage or blown fuses or whatever.

The correct wire to tap into on the factory harness is the illumination wire, the wire that shows 12V when the parking lights or headlights are turned on (red/black on the factory honda harness). If you hook the orange/white from your aftermarket deck up to that wire the only thing that will happen is the deck will dim when you turn your lights on.

Now, if you hook up the orange/white (aftermarket) to the dimmer wire or negative illumination wire on the factory harness there will be bad things that occur. If you just hook up everything that is orange together (a very common rookie mistake) bad things will happen.

I have installed hundreds of radio with the illumination wire hooked up and have not had a problem (and I'm not shitting you when I say hundreds). In my personal car I only wanted the deck to dim when I had just the headlights on (not parking lights), this is what I did with a relay:
85: (thru diode) to blue/red (-) headlight output in steering column
86: 12V or ignition power
30: 12V or ignition power
87: output to illumination wire on aftermarket deck

If you don't have a multimeter or other tool for testing circuits you may want to stay away however due to the possiblity of causing damage you can't fix. In fact, you probably shouldn't be installing an aftermarket radio at all w/o a meter but that's another story.

yeah the only reason its a big deal is that circuit is not fused, so you can potentially fry all your dash light circuitry and replacing the bulbs will not fix things.

yeah, that was a stupid mistake that honda overlooked. but eh, more reason to swap to the 03-05 cluster if you fry it

Needless to say it's been over 7 years since I've messed with my Civic's h/u.
Well, like a fool, I went ahead and accidentally used the dimmer wire on the metra harness instead of the illumination, and I seemed to have fried my dash's dimmer controls.
How am I certain? Well, I certainly had some smoke. And luckily, the dash lights do still seem to work, however my dimmer **** no longer brightens the dash. It's stuck at the lowest light setting.

Could I repair this? Would I be wasting my time removing the cluster?
I realize its been more than a couple years since the post, but any suggestion as to what I should do, or perhaps what you did, would be greatly appreciated.

Thanks again!

well said. good info on the +/- though for the illumination. anyone that does a headlight mod knows that we have ground switched headlights while most other cars are + switched. guess this is the same type thing. my POS Pioneer HU is about to die and i want an Alpine double DIN. maybe i'll try the mod for the dimming on that. thanks man!

"Could I repair this? Would I be wasting my time removing the cluster?
I realize its been more than a couple years since the post, but any suggestion as to what I should do, or perhaps what you did, would be greatly appreciated"

Some have reported locating the dimmer section of the cluster and said they found a trace that was open and were able to repair the trace. (you could have a different situation ?)

Thanks Craig.. I'll check that out, and hopefully that's it. I still have all lighting its just real dim. Perhaps the trace behaved as a fuse and that's why the damage ended there.

Much appreciated!

I'm hooking up a Pioneer DEH-P3100UB using the Metra wiring harness to an 01 Civic GX and I had already made the connection of dimmer on the HU to dimmer on the wiring harness (orange/white to orange/white). Luckily haven't gone and plugged it all into the car yet.

To confirm, I should be hooking the orange/white dimmer wire from the Pioneer HU side to the solid orange illumination/dash light wire on the Metra harness - correct?

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Have you found the problem

I'll go ahead and answer your question for you, since iDevin hasn't logged onto the site in over 5 years.

Technically, yes you would. However, in the past, many (if not all) of us have left that wire disconnected while installing aftermarket head units. There have been far too many cases where people fried some dashboard illumination circuits by hooking that wire up. Leave it disconnected and just let your head unit stay fully illuminated regardless of dashboard illumination setting.