I've tried to connect my Tour to the aux input on my car, a stereo in my home, and a boom box. I used a different cable for each and all were 3.5mm. No matter what I've tried, the phone doesn't recognize that there is anything plugged in.

Clearly, it's not likely that the problem is the cable or device I'm connected to (since I've tried 3 of each.) The Blackberry branded stereo headset that came with the phone works fine, so it's not likely to be the jack on the phone.

Is there a setting that I'm missing?

I just used mine with aux input in a friends car yesterday so I know it works.

I did have my volume turned way down on my phone though and I couldn't hear anything until I turned it way up. Try that.

mine rocks my car radio

Wirelessly posted

One thing I notice (on the 8900, at least), the volume level from headset output is very low. I have to turn the volume on the stereo almost all the way up to be able to hear anything.

Are you saying that it still plays audio through the built-in speaker even when connected? Are you sure that the cable is fully seated?