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I'm installing a remote car starter and it requires me to connect to the +12V and GND wires going into the OBD2 wiring harness.

I can cut the wire inside the car and then splice an additional wire but that doesn't seem to be very clean?

I know they sell "T-Taps" that bite into an existing wire to allow an additional wire to be connected but I've heard bad things especially since they aren't soldered.

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  • \$\begingroup\$ Crimps are more reliable than soldering WHEN DONE PROPERLY. That's the catch. \$\endgroup\$
    – DKNguyen
    Commented Nov 19, 2019 at 21:53
  • \$\begingroup\$ Cut and solder allows heat-shrink sleeving over join. | If you do not wish to cut wire: Use sidecutters or sleeving cutter to cut a ring in outer insulation without cutting wires at all. Practice helps. Now pull outer clear of cut say 5-10 mm. Wrap a tail of Tee in wire around bare inner then solder Tee in place. Insulate. P;ace enough insulation tape around join to mechanically de-stress join. || $400 crimping tools with matching connectors generally work well. | $1 - $100 crimping tools less or much less so. I ALWAYS solder automotive crimps after crimping. YMMV. \$\endgroup\$
    – Russell McMahon
    Commented Nov 20, 2019 at 4:21
  • \$\begingroup\$ For internal wiring (i.e. not exposed to excessively damp conditions) you could use spring-loaded terminal blocks (e.g. Wago 222 series) which allow several wires to be easily and reliably connected together \$\endgroup\$
    – NMF
    Commented Nov 20, 2019 at 15:48

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The "cleanest" way is a tin soldered heat-shrink sleeved connection.

Other ways must guarantee a gas-tight connection between the wires contact surfaces, which can corrode over time.

enter image description here

I have not tried these IDC crimps, but with the plastic threaded lock nut to seal the IDC crimp under pressure, I would support use of these but never any other crimp connectors not rated for automotive use with reliable crimp force and moisture block.

enter image description here

https://www.posi-products.com/instructions1.html

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  • \$\begingroup\$ Soldering increases the risk of wire fatigue and failure with movement - automotive connections should be crimped \$\endgroup\$
    – NMF
    Commented Nov 19, 2019 at 21:56
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    \$\begingroup\$ Strain Relief such as tie wraps or cable string wrap prevents vibration induced strain. \$\endgroup\$ Commented Nov 19, 2019 at 21:58
  • \$\begingroup\$ I think soldering is good enough for diy, non safety issues. The car is probably old and the solder might outlive the car and the owner is savvy enough to repair if broken. It's not fit for a professional. \$\endgroup\$
    – Christian
    Commented Nov 19, 2019 at 22:01
  • \$\begingroup\$ Having repaired many car wiring looms after fire damage, the soldered joints take less space when done properly compared to crimps.. \$\endgroup\$
    – Solar Mike
    Commented Nov 19, 2019 at 22:44
  • \$\begingroup\$ Sorry - Maybe I didn't explain properly ... I need to attach a new wire to an existing wire (i.e. a "Y" or "T" connection). \$\endgroup\$
    – SofaKng
    Commented Nov 19, 2019 at 23:20

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