Just got my deck put in with the GMOS-LAN-03 adapter to retain my OnStar, and I noticed an issue with the instructions.

For those of you new to these things, it has a 30-pin plug that mates with the factory wiring. That goes into a 12-pin plug which plugs into the adapter box. You then have a 14-pin plug coming out of the adapter box that goes into your new deck. However, your deck also needs to connect to wires on both the 12-pin and 30-pin plugs as well. I assume they routed as little as possible through the adapter box to keep it cheaper, but it results in a pretty complex mess of wires by the time everything is hooked up.

The 14-pin output plug is where you connect switched power, amp turnon, mute, and the front speakers, as well as the three wires for the nav system. You get the constant power and ground from the 12-pin input plug. You get the back speakers directly from the 30-pin plug at the factory wiring. The instructions also say that you use the 30-pin's orange and orange/white for illumination and dimmer. My deck has a single orange/white wire labelled as illumination but described as dimmer.

When I hooked my deck's orange/white up to either the orange or orange/white at the 30-pin plug, it did not react at all to turning my lights on and off. There is also an orange/white wire on the 14-pin output plug, which did work properly for me. This may be related to my base model car (no RAP available anywhere on the fusebox, etc.), but I thought it might affect others and I didn't see anything like this posted already. I had to take mine back apart anyway to put the antenna adapter in, but hopefully it can save someone else having to tear their stuff out again.

 

are you trying to set up a dimmer?

 

Well, after using this for a while, I've noticed an issue. When I turn the lights on, the head unit dims down to "night mode" like it should. However, when I turn the high beams on, the head unit goes back to full brightness.

Since I'm using the orange/white wire coming out of the adapter box, my assumption is that something isn't quite right in the box, causing it to provide the dim signal only when the regular beams are on, not the high beams. I haven't actually pulled it apart yet to look at the details of that orange/white connection inside the box to see if there's a way to work around it or wire up some alternate fix.