How do I make stereo display not dim when my lights are on?

[thefultonhow]

I drive with my lights on no matter whether it's dark or stormy or perfectly sunny out. The lights provide better visibility for other drivers no matter what the conditions are, and I don't have to remember to turn them on when I turn my wipers on so I don't get a ticket. Plus, one of the great things about Subarus is they shut your lights off when you turn off the car, so you don't have to worry about leaving them on and running the battery down. So I just never turn them off.

There is one problem with this, though -- I can never see the damn clock on the radio when it's sunny out! Especially in direct sun, I have to turn my lights off momentarily to read the clock, because it dims with the lights on. So I'd like to be able to turn the dimming feature off.

Now I read somewhere (can't find the thread now) where Vikash said that there's a wire going into the stereo that controls the dimming feature. My worry is that if I cut this wire (whichever it is), the lights on my radio won't light up at all and I won't be able to see it in the dark. I take great pride in the fact that every single one of my dashboard lights still works, so this would be a crushing blow to my psyche.

So, can I get the clock to not dim when my lights are on without making it so the other lights on the radio don't come on? TIA.

[realfinn]

The thread you read previously is correct. There is a dimming wire that runs to the head unit. When the lights are on it sends a voltage (probably between 5-12 V) to the head unit switching on the dimming feature. While the lights are off the voltage should be 0V with respect to ground. An easy way to figure out if it would make the lights on the radio be off permanintley would be to find a wire schematic for the radio and using your volt meter test the dimming wire (with respect to ground) with the lights on and with the lights off. If the voltage signal is 0V when the lights are off than that means you can remove the wire and the display will stay on. In this case if the voltmeter reads 0V with the lights off it will be the same as if there is no wire in place.

I hate cutting wire harness apart! So what you can do instead (sometimes) is push the pin that is hooked to the wire back through the connector block and tape it up. Then it will still be there and you can reinstall it if you (or future owners) ever want the feature.

I have replaced my stock radio with a custom setup. I didn't use the dimmer wire (I hate when my lights dim too) and it had no problem. I wouldn't expect this to be a hard project.

Hope this helps! PM me if you need any help.

[thefultonhow]

Alright, I pushed the green wire (the one that Vikash's site said would be the Illumination (-) wire) out of the harness, and lo and behold, the lights on the stereo didn't work! Any other ideas?

[Binford]

It looks to me if you supplied that green wire (illumination (-)) a full 12v, everything should stay lit up all the time. Maybe trigger a relay from the illumination (+) wire? Or maybe you don't need to worry about it, and just feed it 12v. I'm just thinking out loud here, anyone wanna confirm?

[thefultonhow]

I've done some research (most of it on Vikash's site) and if you feed Illumination (-) a full 12v, it dims it to the lowest brightness.

I may just have to deal with it until I get a new headunit...

[Binford]

What if you ground it, then?

[thefultonhow]

Errrrr... I can check that, but I'm not especially enthusiastic about clipping the wire to see. Is there any place I can get one of the pins that fits into the harness so that I can test it out without clipping the wire?

[Binford]

Maybe use a paperclip or something? You might wanna wait for V to respond as he knows the system MUCH better than I. I don't want you to fry something just becuase I told you to try something! It seems to me that'll probably do the trick though.

[vrg3]

Unfortunately, there's no way to do what you want without modifying something inside the stereo. There's no way to make it light up the buttons while also having the clock at full brightness. Maximum intensity when the dash lights are on is dimmer than the intensity when the dash lights are off.

The closest approximation would be to install a switch (maybe in the the blank panel to the right of the steering wheel) that interrupts the yellow-with-blue-stripe wire of the stereo. You could hit the switch in the daytime if you can't read the clock.

If you really wanted to, you could rig up a circuit with a photocell to automatically break that circuit when it's bright outside.

[thefultonhow]

I think I'll just save up for one of those sweet Alpine iPod compatible headunits. They seem to have clocks in them and I don't think I have to hook up the dimmer feature if I don't want to. Plus I can throw out my cassette adaptor and cigarette lighter power dongle.

[SVXdc]

First off, are you talking about the stock Subaru radio? If it was mentioned somewhere in this thread, I didn't see it.

Here's a pin-out for the factory radio harness in the Legacy. It shows the car's wire colors for the different model years.

For older Legacies, see this pin-out by Vikash (on his new site). Here's the drawing:

(view is looking at the pins on the car's harnesses, wires pointing away from you)

For quite a few years (even before 1993) Subarus have had two wires for dash and radio illumination:

• "Illumination +" gets +12V when the parking or headlights are on, open-circuit otherwise.
• "Illumination -" changes voltage as you adjust the dimmer knob on the dash. It varies from about 10 volts (with knob at the dimmest setting) down to 0 volts (with knob at brightest setting). Note that this is reverse from many other cars (where 0 volts = dimmest illumination).

The radio illumination lights (and instrument panel lights) are connected between these two lines. So the bulbs effectively "see" a range of 2 volts (dimmest) to 12 volts (brightest).

There is more information in this thread I posted on NASIOC: Stock head unit information -- pin-outs, subwoofer, aux inputs, and more.

After-market radios are fairly simple: Most (but not all) have a single "dimmer" wire. When it gets +12v, the illumination dims slightly. It is not used to power the lights directly (they will work even without this wire connected). If your after-market radio has a dimmer wire, connect it to the Subaru's "Illumination +" wire. On the after-market radio's harness, this should be an Orange wire, but check your radio's manual to be sure. There is usually also a menu option on the radio to enable the dimming feature (or set to always bright or always dim).

To make the factory radio light up with the dash lights, but always be as bright as possible, simply connect the radio's "Illumination -" wire to ground.

I haven't been able to test in a Legacy, but Vikash says that the factory radio's lights are not as bright with the headlights on (with the dash dimmer knob at full bright) compared to when the headlights are off. In that case, you would need to interrupt the "Illumination +" wire during daylight, with either a simple switch or a fancier photocell circuit.

[SVXdc]

The cleanest way to make that mod to your Legacy is to use forward and reverse radio wiring harnesses (one of each). You'll connect those together, straight-through, and plug them in between the car and the radio. You'll be able to break out the two illumination wires to make your modifications. This is the only option that doesn't cut factory wires. You can also re-use the forward harness if/when you get an after-market radio.

The catch is that you need harnesses that have all 14 wires. The harnesses from after-market manufacturers do not include the Illumination - wire (pin 7). However, I've been making ones that do have all 14 pins. See the link at the bottom of my pin-out page.

... Is there any place I can get one of the pins that fits into the harness so that I can test it out without clipping the wire?

I can also supply single wires with contact pins for special cases such as this. Send me an e-mail (again, see link above).

EDIT: I just noticed your signature says you have a 1990 Legacy {somehow your sig wasn't showing up a little while ago. Did you just add it?}. Unfortunately, I don't have pins for the "older style" Subaru radio harnesses (1994 and earlier Legacies). However, I may be able to get forward and reverse harnesses that use the same pins, which you can cannibalize. E-mail me if you're interested. EDIT2: I now have the older style harnesses.