eBay Blue Tooth Adapter HU Head Units

[MadeInJapan]

Has anyone bought this and had success with it?

http://www.ebay.com/itm/Car-bluetooth-Handsfree-A2DP-MP3-CD-Changer-adapter-Volvo-XC70-V40-V70-/121673665654?ssPageName=ADME:X:BCS:US:1120

The reason I ask is because I did...there is no really good way to splice the power wire into the HU's power cable (coming out of the connector) so I stripped a bit of wire on the HU connector and wrapped the wire from this unit onto it...then when I powered everything up, it sounded great!  That was until I turned the engine on- then all I got was engine rumble through the speakers.  I contacted the seller and let him know that I was not really pleased with my purchase and wanted to return it.  This was on my wife's '04 V70..  He responded for me just to keep it and refunded my money- crazy!  Anyway, I bought a Grom and installed it in her car- great sound, no issues!!  So, I got to thinking that the possibilities of why the eBay unit didn't work: 1.  I didn't have a good connection- it was an open wire and should have been enclosed.  2. There is no ground wire on this unit and that's the cause.  Now, my son's '07 S60 could use a Blue tooth adapter and I'm willing to give this unit a try again.  In the meantime, I bought a wire connector from Amazon (the same one that Grom uses to access the power cable on the HU connector) and I'm going to try to hook this up again knowing that I'm going to have pretty much the most secure connection possible.  But, I was wondering if there is a way to ground this thing- what would you do?  Also, if I can't ground it, is there a capacitor or something I could add to one of the wires to get rid of interference if it rears its ugly head again?  Of course, it might hook up and sound fine without a ground- I don't know...but I wanted to inquire before I went to work to get the HU unit loose.  Btw, he has an HU-850.  

Thanks to all of you Volvo audio geeks here- I figured someone here would know!!  

[MadeInJapan]

I'm thinking if I need to add a grounding wire, I'd like to know which one is the ground on the 8 pin din CD Changer input on the back of the HU unit. Does anyone know?  Would it be a bad idea to run a ground wire from the wire going into that spot to the chassis of the HU unit itself,  or am I asking for trouble by doing this? 

[MadeInJapan]

Here is my update- and it's great news!!!

The way that the wire taps into the power wire was the  problem.  Once I got some Posi-taps from amazon. I was able to use the supplied yellow wire and tap into a friend's '06 V70 HU-650.  It worked out amazingly and it sounds pretty much identical to the GROM unit I put in my wife's car.  I would have added this unit to my son's S60 but his head unit somehow had a metal casing around the back of it that would not allow the round connector to plug in (it's at a 90 degree angle unlike a straight piece shown in the eBay picture)...my friend's V70's HU unit had a plastic casing that was sort of in the way, but I snipped off a piece of it making a channel to allow this thing to plug up.   The bottom line is, this works great and I would buy another one if I had a use for it!  The instructions are in poor English (obviously Chinese company) but there wasn't anything I couldn't figure out.  I never tried a USB key, but it should work as would the line-in on the box.  The little mic that came with it is pretty much identical to the GROM mic and it works fine for making a phone call- all the buttons on the steering wheel work too...it's a good unit- maybe not as robust as GROM's but it's pretty close and to be honest, for what you spend, you get more.  I would recommend this to you if you're looking for a bluetooth unit with full control as long as you're staying with units in '07 and older... I believe the '08 went to part fiber optics and takes a whole different set-up??