Need Electrics Help

[Lagotto]

I have a couple of 12v cables in the rear light cluster on my Mercedes which have been cut, long story, and I need to re-join the two ends. I would normally have no problem doing so, but the electrical system is a canbus and I don't want to do anything which could "upset" the system. My question is which method, should I use spade connectors crimped on each end, or solder the wires together, or just twist them together. I have heard that you need to be more careful than on older vehicles with basic wiring?

 

[Bessy765]

If it is just a case of those two wires being joined together a crimp terminal that has a plastic sheath over it so there is no chance of it causing a short should be fine. Soldering is best if you can but you must insulate them from other wiring. Best to disconnect the batterybefore you start.

 

[Lagotto]

If it is just a case of those two wires being joined together a crimp terminal that has a plastic sheath over it so there is no chance of it causing a short should be fine. Soldering is best if you can but you must insulate them from other wiring. Best to disconnect the batterybefore you start.

The thing concerning me was I have heard people say that slight differences in current/resistance etc can cause problems with things like bulb failure warning etc, 'm no car electrician so it means nothing to me.

 

[autorouter]

There's a dozen ways to do this. Twisting them together will get you home, but is unreliable in the long-term. Soldering is excellent, provided you support the join both sides so it doesn't move, otherwise there is also a long-term reliability problem.

If the wire will hang freely, then a male/female spade terminal will work, but if exposed to the weather may corrode. Better to use a butt connector, crimped on with those red/blue/yellow crimping pliers.

Butt Connectors (Red, Blue, Yellow)

High quality insulated butt crimp connectors in red, blue & yellow for 0.5-6.0mm² cable. Tinned copper conductor & PVC insulation.

www.12voltplanet.co.uk

For a professional touch, slide a length of heat-shrink tubing over the wire (before you crimp the connection!) and then slide it over the butt connector so there's some overlapping at each side. Then shrink the tubing using a hot air gun/hairdryer - a hot soldering iron held near the tubing also works.

True geeks use these, crimp connectors with inbuilt heatshrink to make them waterproof.
Amazon product ASIN B09N39CHS7

 

[autorouter]

The thing concerning me was I have heard people say that slight differences in current/resistance etc can cause problems with things like bulb failure warning etc, 'm no car electrician so it means nothing to me.

If the joint is made properly, it will have very little resistance, less than the variation in the resistance of the light bulbs, so it won't cause any problem.

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[TheBig1]

you can buy heat shrink but connectors. Simply strip back 5mm of wire each end. push them into the connector and apply a heat source to give a watertight and secure joint with near zero resistance. I have used these on many canbus circuits without issue

 

[Lagotto]

Thanks guys, I have the necessary things to make the joint, I was just a bit worried about upsetting the system by choosing a bad method, I will get on with it now.

 

[Lagotto]

Cables joined and insulated, all good, lights checked and all working as they should, thanks for the help.