This guide will take you through the steps involved in replacing coil pack wiring which has become cracked or damaged due to heat exposure. The instructions will guide you through cutting the new and old wiring, and splicing them together using spade connectors. As an alternative, the wiring could be soldered, but I chose to use connectors for simplicity and ease of removal should the need arise.
Note: This guide is provided for a 1.8T AUM, but should be the same or similar for other engines. Please check that the new part matches your old wiring before cutting anything.Cost: <£30
Time: 2 hours
Difficulty: Easy to ModerateYou will need:- Coil pack wiring harness adapter - VW part number 1J0 971 658 M (1J0971658M)
- Wire cutters
- Utility knife
- Flat screwdriver
- Small adjustable spanner
- Multimeter (optional)
- Spade connectors:
- 0.4 to 1mm male (6)
- 0.4 to 1mm female (6)
- 1.1 to 2.6mm male (5)
- 1.1 to 2.6mm female (5)
- Silicone tape (3 metre roll). The one I used is tested to 250 degrees.
- Medium zip-tie (1)
Instructions1) Disconnect the car battery by unhooking the negative terminal.
2) Remove the main engine cover, then remove the three-way PCV pipe, pictured here:
3) Unplug the cables from each of the four coil packs.
4) Unbolt the coil pack earth cable which is next to coil pack 1. Put the bolt back in place for safe keeping.
5) Using a screwdriver, prise the small black tray that the coil pack wiring sits on away from the engine.
The coil pack wiring will now be free. You will see where it enters into a plastic pipe as it disappears down the right-hand-side of the engine.
6) Use a screwdriver to unlatch and remove the clip that is holding the end of this plastic pipe together.
7) With your hand, follow the plastic pipe around 20cm down the right-hand-side of the engine where you will find an identical clip. Leave this one connected to the plastic pipe, but pull its fixing away from the engine to gain a bit of extra freedom.
8) Starting at the top, begin to remove the wiring from the plastic pipe.
Before continuing, count the wires: there should be 11.
9) Identify at which point the insulation of the wiring ceases to be cracked. Using the wire cutters, cut each of the wires at this point. Remove the old coil pack wiring from the car.
10) Cut the surplus plastic pipe so that the shortest wire protrudes by around 5cm.
11) Fit a zip-tie to secure the end of the plastic pipe, in lieu of the plastic clip which was removed in step 6.
12) Strip approximately 5mm from the end of each wire and twist the ends.
You should now be at a point that resembles this (although I hadn't cut the plastic pipe or twisted the ends for this photo):
13) Crimp four of the female 1.1-2.6mm spade connectors onto each of the thick purple/black wires, and a further one onto the thick brown wire.
14) Crimp six of the female 0.4-1.0mm spade connectors onto each of the remaining wires.
That's the car-side of things done. Note that one of my wires had to be cut considerably shorter due to the extent of the insulation damage.
15) Unbox the replacement wiring harness.
16) Remove the first two clips that hold the plastic pipe together, remove the wires from the pipe, and cut the wires at the point indicated.
17) Crimp spade connectors onto the new wiring as per steps 13 and 14, only using male connectors.
18) Match and connect the new wiring to the old.
N.B.
- It doesn't matter which of the black/purple wires you connect to which - they all terminate at a common point.
- There are three wires which are all the same colour brown. The way to tell them apart is by their thickness.
- The four important wires are the striped thin ones - these control the firing order. They do tend to fade, so if in doubt, refer to the wiring removed in step 9 to match the old and new wires correctly.
19) Using 5cm strips of silicone tape, individually wrap each spade connector joint to cover all exposed metal. Stretch the silicone tape as you wrap it.
20) Continuity testing (optional). Using a multimeter, check to ensure that pins 1, 2 and 4 have continuity across all four plugs. There is no way to verify pin 3.
21) Using larger strips of silicone tape, wrap all of the individual wires into one bundle. Start in the middle where the spade connectors are and work downwards towards the plastic piping (overlapping this slightly). Then from the spade connectors upwards towards where the black tape finishes near plug number 4. Again, stretch the silicone tape as you wrap it.
22) Mount the new small black tray that the coil pack wiring sits on onto the engine.
23) Attach the coil pack earth cable to the bolt on the engine.
24) Plug the cables into each of the four coil packs.
25) Push any excess coil pack wiring down the right-hand-side of the engine.
26) Re-fit the three-way PCV pipe removed in step 2 and re-fit the engine cover
27) Re-connect the car battery.
Job done!
Please let me know how you get on, or if you have any feedback to help me improve this guide.