I just finished installing a handsfree kit for my Nokia 8260. The unit is made in Sweden and I happened to stumble across it on eBay. The manufacturer is SmartEQ (www.smarteq.com), Handsfree Pro model. After receiving the unit and reading the instalation instructions, I noticed they had something available called a "ISO Mute Box". Basically, this ad-on plugs in-line to the speakers outputs on the factory deck and attached to the HF "brain" box via a 6-conductor cable (looks like a home telephone cable). I immdiately tracked down the one and only SmartEQ dealer in the US (in Florida) and ordered one. I hooked up the phone mute connector on the factory deck, and everything works like a charm when the engine isn't running.

I have the kit installed in a 1996 C280 with Bose sound system. When the phone is in use, the radio display shows "phone" and the speakers mute. The "Mute Box" has a little amp in it and relays the output from the phone directly to the factory speakers (front only, rears are muted so the mic doesn't pick up an echo).

As I stated earlier, everything works as if it were OEM, except when I run the engine. Then I get a whine through the speakers. Sounds like a ground loop issue, as the whine goes up and down depending on how high the engine is reving. When I installed the system I hooked up the Constant, Switched, and Ground to the corresponding wires on the back of the factory deck. I was worried it would give me issues, but hey it was the easiest to get to since I already had the radio out to connect the mute box. I have already tried to relocate the ground, that didn't help.

Any suggestions on where a good point to get a clean ground, constant 12V+, and switched 12V+ that doesn't involve dismantling half the car or running lines all the way back to the battery? Oviously the ignition would be a good place to start, but I didn't take the time to see what was all involved in removing enough plastic to get at the wiring. It was around 10 degrees here in Minnesota, and my garage was only slightly warmer. Didn't want to risk breaking anything due to the cold.

Any help would be appreciated! If we figure this out, this kit is a great option for someone like myself who doesn't have the steering wheel controls and still wants to integrate a phone through the factory sound system. They make the kit for a whole slew of different phones.

 

go to radios shack and buy a ground loop isolator and see if this helps. get the one used for power and ground connections, not the one used for rca connectors. you also may have to run a wire from your battery negative directly to the unit. also you may want to try this first since this is a freebie. take both the power wire and the negative wire and twist them together. this helps eliminate interference in the power supply. The more twists per inch the better.

 

I also installed handsfree kit in my ML and had similar problem. Here are couple solutions I tried
1. Ground, Ground, Ground - that is usually biggest problem. Make sure that you find a good way to attach ground (unpainted part of body would be perfect, but even good bolt somwhere on the body would do).
2. make sure that control unit of your handsfree kit is as far as possible from the radio itself and any other electrical parts of the vehicle (as much as possible).
3. Keep all the wires short, avoid coils cause they act as antennas.
4. Some aftermarket parts (noise reducers etc.) help too.
5. I draw all the main power and switched power from fuse box. (BTW the fuse box does have great ground - goes right to the battery)
Just my $0.02. I hope it helps. Good luck!