Alternator noise via blutooth dongle ??

[Pukmeister]

Can anyone help??

I recently bought the stereo bluetooth module to fit my Autocom Pro7 Sport. Fitting it required a +12V feed only, the earth presumably is via the stereo jack into the Autocom.

It paired fine with my Tomtom rider (which pairs with my iPhone for calls). I also played music fine via a 3.5mm jack into the other Aux port from my Ipod Nano.

The problem is when cranking the engine there is a whizz,whizz, whizz as the engine cranks, followed by the high pitched background whine when the alternator is spinning with the engine running.

I unplugged the 12 volt bike feed wire from the bikes loom and ran the Pro7 Sport via a 9V battery. The noise was absent, reconnecting the bike power to Autocom brought the noise back. I tried resiting the Pro 7 sport away from the battery but nothing changed. I unplugged the Bluetooth dongles jack plug and the music became crystal clear. Plugging in the Bluetooth dongle brought back the alternator noise.

I suspect the problem is due to the earthing of the Autocom/Bluetooth dongle as it disappears on 9v battery power or when the bluetooth dongle is unplugged.

Can anyone offer a solution on how to cure the electrical noise (other than not using the new stereo bluetooth unit)??

Thanks in advance.

 

[Bumpkin]

Sounds like ground loop interference. Is the BT dongle powered from the same source on the bike as Autocom?

I was warned that I would suffer GLI with my Autocom connected PMR being bike powered. Powered it from the same point as the Autocom and I have no problems. Got this advice from someone who had done the same but hooked both items to different + points on the bike first time around.

 

[Pukmeister]

I initially had the Bluetooth dongle +12V feed coming from the same wire as the Autocom (off the back of the accessory socket). I then moved the wire to my 'Fuzeblock' switched power distribution fuseboard under the seat, fed via the battery terminals. Still the problem remains.

I have an old black Autocom ground loop isolator box and a black/red one which I plugged in but it meant the bluetooth dongles blue LED stopped worked, suggesting the negative connection won't connect properly through it to the Autocom.

At £79 for the Bluetooth dongle, I'm not impressed that I'm getting interference.

 

[Sam@Chainspeed]

There are a few things you can try in order to eliminate alternator / HT noise.

The Bluetooth module can pick up interference either via the power connection or via airbourne noise due to its location.

We have found with the new BT module that quite often if it is powered from the same supply point as the Autocom, it can pick up some noise. firstly try taking the positive wire from the module directly to the battery. If this cures the problem, either try a different switched live or a relay can be used so it draws power directly from the battery when the ignition is on.

Also try moving the location of the module as this can eliminate all noise by even moving it 10cm.

 

[Pukmeister]

I then moved the wire to my 'Fuzeblock' switched power distribution fuseboard under the seat, fed via the battery terminals. Still the problem remains.

As you can see from the above quote Sam, I already tried that.

I may try wrapping the Bluetooth feed cable around a toroid to try and eliminate any RF from the alternator/coils.

 

[Greg Masters]

It's not the Bluetooth dongle. It's the 3.5mm jack that is directly connecting one bike-powered unit (Tom Tom) with another (Pro-7 Sport).

The fix is to put a ground-loop isolator in the line of the 3.5mm jack. See eBay 260741338139.

Greg

 

[Pukmeister]

The Tomtom connects wirelessly via Bluetooth Greg.

I think you are on the right track though, it's the 3.5mm jack on the Bluetooth dongle that goes into the Pro7 Sport. When you unplug it the alternator noise stops. The jack plug obviously completes the ground circuit to power the Dongle as well as carrying the stereo audio.

I have a pair of Autocom ground loop boxes in my garage(one all black, one half red/half black). The black ground loop isolator has a 2.5mm jack which used to be for my old Tomtom Rider 1 rechargeable Bluetooth dongle so I'm gonna try and get an 2.5mm to 3.5mm adapter and see if it works.

Neither port on the black & red unit makes any difference, the Bluetooth dongle fails to power up when I try it. It was for my old Nokia cellphone and BMW Nav2 cradle.

I'm surprised that these dongles have issues with sharing the ground connection of the unit they are meant to plug into, it's not exactly a good design IMO if you need to feck about or buy more leads to get the damn thing to work properly from new.

 

[Greg Masters]

The Tomtom connects wirelessly via Bluetooth Greg.

So it may be - but both your Tom Tom and your Autocom are hardwired to the bike's alternator.

Greg

 

[Pukmeister]

So it may be - but both your Tom Tom and your Autocom are hardwired to the bike's alternator.

Greg

Ah yes, I didn't think of it like that.