I have my pioneer avh-p4400bh headunit installed. I just noticed that when I turn the dimmer switch down the headunit gets brighter, when the interior lights are off the headunit is at its brightest, I thought the dimmer went off of headlamp voltage only? I know someone is going to say it only looks brighter when the lights are dim, but its actually bright I can watch the screen illuminate. So is this normal or am I hooked up wrong some how? Thanks. I have a feeling whitebird will have my answer like he always does.

 

I`m not sure if the p4400bh is any different in that way but my 3500dvd has the same brightness all the time, it isnt connected to the headlight dimmer switch at all..
I`m guessing the stock HU`s had that dimming feature and yours is just hooked up wrong ?

Hopefully whitebird will have a more specific answer but talking from my personal experience, my pioneer HU doesnt do that..

 

There are two illumination wires in the standard wiring configuration: orange and orange/white. They are similar but perform slightly different functions. The orange wire is designed to receive variable voltage from the dash light dimmer output so that the head unit can change illumination brightness in sync with the rest of the dash lighting. The orange/white wire is designed to receive a simple power/no power (on/off) voltage from the parking light output to determine if the lights are on and then adjust display brightness based on its own settings. These wires correspond to the gray (dimmer) and brown (parking lights) wires in the factory harness.

I suspect that you have the orange/white wire connected to the gray wire in the factory harness. Or, if you used a harness adapter (as you should), you have the orange/white wire from the head unit connected to the orange wire in the harness adapter.

What happens is the head unit is expecting a simple on/off voltage through that connection... on when the headlights are on so dim the display, off when the headlights are off so brighten the display. Instead, you are giving it variable voltage from the dimmer. It sees higher voltage (on) with the dimmer turned up so it dims the display assuming the headlights are on. It sees lower voltage (off) with the dimmer turned down so it brightens the display assuming the lights are off. It has only two settings - on or off - so that transition would happen at a certain point in the dimmer settings where the voltage becomes low enough that the HU considers it "off".

 

I did use a harness adapter I would never cut the wires to a factory harness. So would you advise just disconnecting the dimmer wire since it only works on the running lamp voltage and the running lamps are always on this car anyways, and I seem to have it connected incorrectly.

 

Why would the running lamps be always on? If you mean the Daytime Running Lights (DRLs) on the front, they are not part of the parking/running light circuit - they are handled separately by the DRL module under the dash.

Just disconnect the orange/white radio wire from the orange adapter harness wire and reconnect it to the orange/white wire in the adapter harness.