Tomtom 910 + 2004 Aux Input

[vicious]

I have a Tomtom 910 and a 2004 Mini

I installed the aux input by making a connector out of an old computer cd audio cable and wiring that to an 1/8" female plug. This works fine with my ipod plugged right in, and it works fine with other mp3 players.

When I plug my TomTom mount's speaker out into the Mini aux in, I never see the "aux" mode when pushing the Mode button.

So I tried playing an mp3 to create a signal, plugged in the cable. No sound from 910, so the 910 thinks the speakers are plugged in. Cycle the modes on the headunit.. nothing. Then I tried Pulling out the cable. 910's speakers start playing the music fine. I then plugged the cable back in, and quickly cycled the modes and there it was, "AUX" and I could hear sound coming from the 910, for about 5 seconds, and then aux mode disappears again, but the 910 still thinks it's connected.

So the initial plugin of the cable makes the headunit think there's something there, but it soon "gives up" and turns off Aux mode. What I'm wondering, is if the 910 isn't sending enough volume, or if there's some option to 'boost' the line-out. In-case it makes a difference, I'm using the suction cup mount that came with the 910. I was wondering if anyone has seen this problem before.

I'm planning on getting a little headphone amp and seeing if that makes a difference, I'll post here once I try that.