GPS 478 music volume

[JOHNF]

I currently have a Garmin GPSmap 378 that I will be switching to the 478. (So I can download routes from MapSource to the GPS)

I have the XM Sat radio hooked up and running, but need to be able to control the volume of music separate from the Volume of voice prompts.

I have an '05 but am unable to identify what BMW Com system that I have...I know it is not the stock com system for the 2005, but the system that preceded it.

Right now the volume for the stereo from the GPS is controlled with the volume slider on the GPS unit. At the lowest setting the music is too loud for me (and I have hearing loss and wear ear plugs). Also, at the lowest settings it is very hard to hear the R Ear only mono voice prompts. The mono sound output for voice prompts is integrated in the power lead.

Does anyone have a set up that lets the BMW com system and the Volume control on the handlebars control the volume of the XM stereo lead (it is a separate wire that is plugged into the back of the GPS unit and then runs to the Com System...but I have no idea what port)?

The question is: How do I control the volume from the GPS stereo lead for the XM radio with the bike's handlebar volume control button?

TIA

[messenger13]

This may or may not help you. On all of my devices, I always install this crappy little inline volume control from RadioShack (http://www.radioshack.com/product/index.jsp?productId=2102975&cp). It's only $7.99 (some stores sell it for $6.59) and is pretty darn impervious to rain, as I have yet to have one fail on me. I have one on my Garmin 2720 (otherwise it's WAY TOO LOUD), my iPod, and the receiving end of my cell phone. Perhaps you could put this inline out of your GPS or XM radio, or both.

[charlieg]

GPS stereo leads to a FM modulator works well for me in use with my 376c with the built in XM radio. You can control the volume as you would with the bikes FM radio and the GPS voice prompts will override the XM. Only down side is if you are not listening to the XM you will not get the GPS voice prompts. I also got very little volume when I connected the mono voice leads to my Autocom. -Chuck-