Rep Power: 198

I was in my car last night (2003 civic ex coupe) and was playing around with the dimmer when my friend pointed out that the headunit was dimming aswell as the backlights.

Btw my HU is some like 5 or 6 year old JVC crap deck that i'm replacing this summer. But it came with the car so no complaints ...

Anyways, I was so confused because i always thought that you weren't supposed to connect the dimmer when you install a HU because it messes everything up. So far nothing seems weird, except for the lighting on my AC and the cirrculate air button or whatever don't light up unless i tap underneath the HU a couple times then the lights will either flicker or come on for a bit.

 
Rep Power: 313

You arent supposed to connect it to the dimmer.... if you had it professionally installed the installer may have connected it though. I'd honestly take it apart and disconnect the wire.

 
Rep Power: 0

I think the reason most people have a hard time with the dinner wire is because they don't really understand what they're doing. Their friend or a message board or someplace told them to hook up some wires, so they don't do the first thing you need to do when do any sort of wiring:

Check the voltages yourself.

Call the manufacturer (if the instructions aren't clear) to determine what you should do.

If you can't do a minimal amount of testing and research about how to do it, then you'll be better off paying someone $200 to hook it up, because if you screw up a wiring harness, you'll be paying a garage 3x that amount to trace the problems and replace parts of the harness.

If he paid an professional installer and it works, there's no reason to remove the dimmer feature. The head units are designed to dim when the lights are turned on. Its a significant safety feature, and its a great convenience feature.

 
Rep Power: 0

When I see people say check the voltages...I get a little concerned. When you have the whole dash removed to get at the head unit you have exposed SRS components...If you mess one of those up you have to get your error code reset....Everything i read for installs says battery disconnected. How are you checking voltages on the harness if you have your battery disconnected? A DIY head unit install should NEVER have the battery hot when working in the dash.

 
Rep Power: 0

The SRS harnesses in Hondas (indeed in most cars) is a separate harness. This harness is wrapped in yellow coating, and basically it means "caution stay away". Even with the battery disconnected, I stay well clear of that.

As to how you check voltages, yes indeed, you do the install with the battery disconnected. At the point where you have it almost buttoned up, you do a quick connect and check the voltages. Then you disconnect again.

If you're uncomfortable doing that (which is fine), then I question doing any work in the dash in the first place. Of course, I see guys doing stuff like twisting wires by hand and then wrapping this with some black electrical tape. And after about 3 months the tape falls off because that tape is not designed for that type of application (solder and shrink wrap is what you should be using) and then nothing works, and then guys have to tear the dash apart again, because they wouldn't take 30 minutes to do the job right.

I say all this because I know guys do lousy and dangerous installs all the time. And so this becomes folk wisdom that "you should never connect the dash wires to the head unit", which is false and comes from people not understanding what they're doing. To be fair, I've called places that claim to have "professional technical help" which is basically a lie, so its hard to get good information. But not impossible. The manuals for almost every Honda are available online and all of these have wiring diagrams which can be followed if you have the patience.

Research the problem, be willing to make a mistake and fix it, or pay a professional to do it.

 
Rep Power: 198

I guess he had it professionally done because it works fine so no complaints here ... but i'm getting a new deck this summer (hopefully) so it doesn't matter anyways :P Thanks for ur answers guys.

 
Rep Power: 307

I was able to use the dimmer lead fine on my Pioneer. I was able to use the red/blk to dim my vacuum fluorescent clock as well.

Can't be sure just what people are doing but, when it goes wrong it can go very wrong for certain.

They most likely leave out key parts of the story when they make the thread (larger fuse installed after finding 1st one blown, connecting dimmer wires wrong or together, not isolating unused wire ends etc)