Hi Folks,

A few months ago I installed an X920BT in my 2008 Hummer H3 using the GMOS-01 adapter to retain OnStar and chimes.

Everything about the install works great except for the day / night mode on the X920BT. I checked and double checked my connections according to the X920BT and GMOS-01 installation guides and they are correct; however, night mode still does not work.

I have Googled around and searched on this forum and have read that the illumination wire / circuit on the GMOS devices do not work and that the solution is to hard wire in to the illumination wire of your vehicle. The problem with the H3 is that the illumination wire comes over the CAN bus and is not a regular 12v signal wire.

I figured I could just tap into the dimmer wire going to my HVAC controls (which is a 12v wire) to achieve the same effect as the illumination wire, but I read somewhere on this forum that it could potentially brick my X920BT if the dimmer switch is used.

Is it safe for me to use the dimmer circuit on the H3 to get the headunit to switch from day to night mode? If not, is there another alternative for me?

Thanks.

I'm also wondering about this. I'm installing a X920BT in my 2007 Tahoe with a PAC OS-4 harness. I have factory navigation in my Tahoe now, and it automatically changes to a black background when the headlights come on, so I'm assuming that that it is receiving and illumination feed from somewhere. I've read so many forums about people who can't get there illumination wire to work. Has anyone had experience with the illumination wire on the PAC OS-4?

Hi Folks,

 

A few months ago I installed an X920BT in my 2008 Hummer H3 using the GMOS-01 adapter to retain OnStar and chimes.

 

Everything about the install works great except for the day / night mode on the X920BT. I checked and double checked my connections according to the X920BT and GMOS-01 installation guides and they are correct; however, night mode still does not work.

 

I have Googled around and searched on this forum and have read that the illumination wire / circuit on the GMOS devices do not work and that the solution is to hard wire in to the illumination wire of your vehicle. The problem with the H3 is that the illumination wire comes over the CAN bus and is not a regular 12v signal wire.

 

I figured I could just tap into the dimmer wire going to my HVAC controls (which is a 12v wire) to achieve the same effect as the illumination wire, but I read somewhere on this forum that it could potentially brick my X920BT if the dimmer switch is used.

 

Is it safe for me to use the dimmer circuit on the H3 to get the headunit to switch from day to night mode? If not, is there another alternative for me?

 

Thanks.

If you tunrn your headlights on and your HVAC controls/display illuminate/dim, it would be safe to tap into that wire for your illumination wire.. It is the same as your illumination wire going to your stock radio, which if you get a pin out diagram, you can tap into that wire also..

Odie

If you tunrn your headlights on and your HVAC controls/display illuminate/dim, it would be safe to tap into that wire for your illumination wire.. It is the same as your illumination wire going to your stock radio, which if you get a pin out diagram, you can tap into that wire also..

 

Odie

most of these new cars do not have the standard illum wire, all the modules (radio's, climate controls, and guage clusters...) get the dimming signal from the vehicles can-bus system, and the data modules that come with all of these expensive wire harnesses are supposed to decode the diming signal from the can bus and convert it to something that the radio will understand. however there are a few vehicles that this doesnt work for (havent really been able to get a reason why) but you will need to find somewhere else to get the signal, if the car does not have auto lights, then you can tap into the parking light wire from the switch(only if positive trigger) or you can tgo to any dash light(it would have to be one of the wires for the light bulb itsself, like an ashtray light) or if all else fails, as a last resort you can go and run a wire to one of the parking lights or headlights themselves (if the car uses negitive trigger, then you would have to use a relay to switch the polarity)

most of these new cars do not have the standard illum wire, all the modules (radio's, climate controls, and guage clusters...) get the dimming signal from the vehicles can-bus system, and the data modules that come with all of these expensive wire harnesses are supposed to decode the diming signal from the can bus and convert it to something that the radio will understand. however there are a few vehicles that this doesnt work for (havent really been able to get a reason why) but you will need to find somewhere else to get the signal, if the car does not have auto lights, then you can tap into the parking light wire from the switch(only if positive trigger) or you can tgo to any dash light(it would have to be one of the wires for the light bulb itsself, like an ashtray light) or if all else fails, as a last resort you can go and run a wire to one of the parking lights or headlights themselves (if the car uses negitive trigger, then you would have to use a relay to switch the polarity)

My bad... Ya learn something new every day.. Here I thought my 05 Ford was new.. I guess I'm just dillusional.. LOL

Odie

yea FoMoCo cars are usually the easiest to find a illum source, but GM's are one of the hardest since they have been using the can system the longest and are the most intergrated, while fords has just recently switched over to can controlled radios in the last couple of years.

man the good ole days of this stuff being easy are slowly slipping away

Has anyone had any success with a 2007+ Tahoe/Yukon/Suburban and a PAC-OS4? I've read some forums saying that the illumination wire will work and that it won't. I'd be up for just trying both, but pulling the radio in and out of the dash isn't the easiest thing in the world with all those wires, so I'd like to get it right the first time.

The only thing that makes me think that the newer body style Tahoe's will have a working illumination wire is that on my Tahoe(I have factory nav), when the headlights turn on, the navigation map automatically turns black, so the radio is somehow getting a feed from the headlights. Hopefully it is from the orange illumination wire.

Tahoe(I have factory nav), when the headlights turn on, the navigation map automatically turns black, so the radio is somehow getting a feed from the headlights. Hopefully it is from the orange illumination wire.

this is because the factory nav is hooked into the CAN-BUS system, it can read off of the comands that the cars computer sends. there is no illum wire at the factory radio harness, however the module for the wire harness (PAC) decodes the CAN signals from the BUS wire and then converts them to a standard 12v+ trigger on the module's illum wire, the problem here is that some time the module does not propperly decode all of the signals propperly and it seems to be a random issue, probably having to do with slightly different firmwares.

this is because the factory nav is hooked into the CAN-BUS system, it can read off of the comands that the cars computer sends. there is no illum wire at the factory radio harness, however the module for the wire harness (PAC) decodes the CAN signals from the BUS wire and then converts them to a standard 12v+ trigger on the module's illum wire, the problem here is that some time the module does not propperly decode all of the signals propperly and it seems to be a random issue, probably having to do with slightly different firmwares.

So when you say "some times the module does not properly convert the signal," do you mean on some certain vehicles it just won't work (i.e. it may work on this Tahoe, but not that Tahoe), or do you mean that it will sometimes work in your car and sometimes it won't work on your car (i.e. day-to-day it wcould be work or not work)?

The truck has auto headlights, when they come on all the HVAC controls illuminate. There is a rotary dimmer switch that I can dim the HVAC lights with if I so choose.

I know exactly which wire sends the 12V signal to these lights... if I tap this wire I should be safe even if the dimmer is used?

The truck has auto headlights, when they come on all the HVAC controls illuminate. There is a rotary dimmer switch that I can dim the HVAC lights with if I so choose.

 

I know exactly which wire sends the 12V signal to these lights... if I tap this wire I should be safe even if the dimmer is used?

If you are trying to dim the radio display like your HVAc controls by using your dimmer knob, I don't think it will work as the radio is not capable of illumination dimming like your HVAC controls.. For instance, on my truck when the headlights are on the map dims to a predetermined level and the skyscape goes from light blue to dark blue with stars.. If you have a manual hedlight/ marker light switch, as I do even with auto headlamp, you could tap into that to use as your illumination wire to your stereo..

So when you say "some times the module does not properly convert the signal," do you mean on some certain vehicles it just won't work (i.e. it may work on this Tahoe, but not that Tahoe), or do you mean that it will sometimes work in your car and sometimes it won't work on your car (i.e. day-to-day it wcould be work or not work)?

in every sense of the words, like i have done many 04 tahoes, but the one i did last week, none of the door chimes worked (which is one of the main points of the harness) everything else worked just fine and i even tried two different modules. there are a few cars that dont ever seem to work at all, then you run across a car that should work great and then it just doesnt. its so weird, that there is no cut and dry "will it work" list of cars which makes be believe that there are also just very small differences in the car programs.

Been having the same issues with my X920BT also and wasn't having any help here. So I asked around on my TBSS forums and got an answer almost instantly for my truck. I just tapped into an illumination wire on the rear wiper controls. Nice and easy since my wiper controls are right next to the stereo. You could probably do the same thing for a tahoe, yukon, etc.

Here's a pic too:

Sweet.....bout to do this on my TBSS....thanks!