Car Audio: How to split power/ground leads?

Ernie Ball

I'm trying to add a bluetooth handsfree unit to my car stereo. The problem I have is: this unit (an Alpine KCE-300BT) needs to be connected to the power, ground and ignition leads. But these are already connected to the head unit.

Is there a way to split these leads so that both the head unit and the bluetooth unit get power, are grounded and are connected to the car's ignition?

I don't want to run a new set of wires to the battery, since the bluetooth unit is small and doesn't require much power.

Anyone know what I should use and where I can get it? Thanks.

Marcus.Aurelius

TBH, I would ask in Halfords. The Liffey Valley crowd seem fairly knowledgeable in this regard. If you know any electricians, you can get some splitters very cheap.

You'll need some fuses too, to protect the new line and unit, most stereos are 15 A fused through the main line and 10 A at the back as a secondary.

crosstownk

Cut the main cable and use crimp connectors to connect the two cables in a Y set up. Remember that you need a good electrical connection and a good mechanical connection - you don't want the wires to eventually come loose. I've seen many phone/stereo fitters simply strip back the insulation on the original power cable and wrap the additional cable around the exposed wire, but I'm not a fan of this. Be sure to insulate any exposed metal. You should also have a fuse on each branches from the main cable. One for the HU and one for the bluetooth. There should be an inline fuse on the wiring kit for the bluetooth and I'd hazard a guess that an Alpine HU has an inline fuse on both the +12VDC and the +12VDC(ign) wires.

No need to split the ground. Just attach the -12VDC of the bluetooth kit to anything metal - you may be able to locate an earth point somewhere under the dash. Grounding in this manner reduces the possibility of interference.

DublinDilbert

I'd just use 3 "snap lock" IDC (insulation displacement connectors) splices, they allow you to splice each of the 3 new wires into the 3 existing wires, without cutting the existing wires. They can also be removed when your taking out the car kit

The existing wire just passes straight through this connector and a metal gate pinches either side of the wire and makes an electrical connection

You can get a bag of these in maplin for around €2, here's a link:-
http://www.maplin.co.uk/Module.aspx?TabID=1&ModuleNo=1073&doy=15m8
http://www.maplin.co.uk/Module.aspx?TabID=1&ModuleNo=43076&doy=15m8

From maplin:-
The easiest way to connect a new cable to existing wiring - ideal for in-car use. Slip the connector over the existing cable, where is snaps into place, then place the new cable into the connector and fold the top over. A quick squeeze with the pliers is all that is needed to permanently lock the connector in place and make a sound electrical connection. The red type suit cables from 0.4mm to 1.0mm, the blue type suit cables from 1.1mm to 2.6mm and the yellow type suit cables from 2.5 to 6.5mm. Made from PP plastic with tin-plated brass terminals.
Supplied in packs of 10.

JohnCleary

crosstownk wrote:

I've seen many phone/stereo fitters simply strip back the insulation on the original power cable and wrap the additional cable around the exposed wire

Nothing wrong with this so long as the connection is soldered and covered up nicely after

crosstownk

I've seen lots of these snap-lock connections used - not really the best solution. I've had many a wiring problem with towbar wiring because of these clips - I suppose the fault could also have been the installer. I've fitted many high end stereos and I would never use these things. I've seen wire break and fall loose with them. If you do use them then be 100% sure that you are using the right snap-lock for the cable size, as posted above.

Ernie Ball

crosstownk wrote:

Cut the main cable and use crimp connectors to connect the two cables in a Y set up.

Not sure how this can be done with crimp connectors. How do I get 2 from 1? Can you explain? Or should I just use the snap connectors mentioned by DublinDilbert?

Can I also do this to the ignition lead?

You should also have a fuse on each branches from the main cable. One for the HU and one for the bluetooth. There should be an inline fuse on the wiring kit for the bluetooth and I'd hazard a guess that an Alpine HU has an inline fuse on both the +12VDC and the +12VDC(ign) wires.

Head unit only has an inline fuse on the power wire. The installation manual for the bluetooth unit says nothing about needing a fuse. Am I wrong to think that the single 10A inline fuse should be enough if it's upstream from the split?

Ernie Ball

DublinDilbert wrote:

I'd just use 3 "snap lock" IDC (insulation displacement connectors) splices, they allow you to splice each of the 3 new wires into the 3 existing wires, without cutting the existing wires. They can also be removed when your taking out the car kit

The existing wire just passes straight through this connector and a metal gate pinches either side of the wire and makes an electrical connection

Just the sort of thing I was looking for. Cheers!

In fact, I think I was looking directly at a bag of these at Halford's today. D'oh!

crosstownk

Ernie Ball wrote:

Not sure how this can be done with crimp connectors. How do I get 2 from 1? Can you explain?

Basically the connector is a small cylindrical thing - you simply insert all the relevant wires into it and crimp it.

Ernie Ball wrote:

Can I also do this to the ignition lead?

Yes.

Ernie Ball wrote:

Head unit only has an inline fuse on the power wire. The installation manual for the bluetooth unit says nothing about needing a fuse. Am I wrong to think that the single 10A inline fuse should be enough if it's upstream from the split?

Personally, I'd prefer to have each accessory on it's own fuse - apart from the added protection, it make fault diagnosis easier. It also means that if one accessory blows a fuse you won't be without the other. But the key is to have the fuse ratings smaller closer to the accessory without dropping below the minimum required for any given accessory.

JohnCleary wrote:

Nothing wrong with this so long as the connection is soldered and covered up nicely after

Agreed - but in this instance soldering is a must. Not to many phone/stereo installers use solder

crosstownk

Sorry - duplicate post. Damn this irregular server behaviour!

JHMEG

I second DublinDilbert's suggestion. The snaplock connectors are very quick and easy. Fitted properly they should not come off.

All good motor factors have them, and Halfords have them too.