So I decided I wanted to do a full wire tuck, I've always hankered after a "show car" engine bay and thought it would also be a good opportunity to learn more about the bit of the car that I'm not that familiar with - the wiring! I've used the DIY guides over on Vortex as a great starting point, but I have found in my early days that whilst the guide is spot on, it is based on a LHD car plus omits a few specific steps/instructions that I would have found useful. To that end I'm going to try and write up a DIY as I go, split into smaller, manageable sections. I'll also try to add photos in retrospectively once I've figured out how to get image hosting working now that Photobucket want you to upgrade your account for third party hosting
Wire Tuck Phase 1 - Drivers Side Wing AreaThe following wires are present here;
- Drivers side (RH) headlamp unit. 10 wires in total controlling the headlight motor, main beam, dipped beam, foglight and indicator. OEM route is out of the cowl panel just to the right of the strut tower as you look at the engine bay, then underneath the coolant ball, down the inside of the wing and then across behind the washer bottle. Most of the wiring is in a corrugated tube and is routed through a couple of plastic formed "runners" - one by the base of the washer bottle and one behind the coolant ball.
- Bonnet catch sensor. 2 wires that follow the same routing as the RH headlamp as above.
- Washer bottle pump motor. 2 wires that lead into the same routing as the RH headlamp as above.
- Washer fluid level. 2 wires that lead into the same routing as the RH headlamp as above.
- Brake Fluid Level Sensor - 2 wires that run a short length from the grommet to the brake fluid reservoir.
- Coolant Level Sensor - 2 wires that run to the side of the coolant ball.
- Air-Con Pressure Switch (I have simple A/C on my model, not the clima-control which may be different) - 3 wires that run along the bulkhead and into the air-con hose located approx. midway along the engine block at the back of the bay. Covered with a fabric heat shield secured with 3 press-studs.
***All of the above wiring systems run into the upper rubber grommet at the cowl panel. Also note the front and rear washer hoses run from the washer bottle (obviously!) and into the harness alongside the wires.
- Finally the ABS senor cable runs into this upper grommet. It appears as 1 wire (noting that it actually contains double sheathed twin wires) and resembles a black silicone hose roughly the same diameter as you would use for a washer jet or vacuum hosing in the engine bay. This runs from a plug on the wheel hub via the clips mounted on the suspension (my AP coilovers have the correct OEM tabs as part of the strut body), through a grommet in the inner wing and then into the wiring harness back to the upper grommet at the cowl panel.
There is also a lower grommet at the cowl panel, with the following;
- EVAP canister connector - 2 wires that plug into the top of the black plastic charcoal canister.
- Exhaust pre and post CAT sensors.
ProcessThe process I followed went something like this noting that I plan to relocate the washer bottle to the boot and already have the EVAP system removed.
1. Unplug all harness connectors and unbolt/unscrew the fastenings holding the coolant ball and power steering reservoir so you can move these around and give you a bit more space to work with.
2. Remove the washer bottle, remembering to disconnect the two washer hoses and pump harness. This is easier if it's empty, however if you leave the pump and sensor in the bottle you can just about get away with it like I did
3. Unclip the harness from the plastic runner down where the bottom of the washer bottle used to be. There will be two hard pipes to the right which are for the aircon system, leave these be. You will need to then cut any tape holding the harness to the runner and bin the runner.
4. Continue to chase the harness back and remove it from the small o-clip attached to the inner wing. Keep going and unclip from the plastic runner that sits on the strut tower. Note this is tight between the strut tower and the brake fluid reservoir so be very careful not to force this out the way too much as you really don't want a damaged brake system. This was a pain but with a bit of wriggling it comes out easy enough. You can then bin this plastic runner too.
5. You should now have a harness that runs into the upper grommet at the cowl panel, noting the ABS sensor wire gets added into the mix near the top. Get back to the headlight and start striping the corrugated tubing and any harness tape off so you're left with loose wires.
6. Optional - for reference and for my own knowledge I then got the trusty Haynes manual out and verified I could trace everything back to the wiring diagrams at the back using the colour coding of the wires and the pin numbers on the connectors.
7. Remove the cabin filter housing panel at the passenger side (4 small black +ve screws), windscreen wipers (prepare for a battle) and windscreen cowling panel. There's enough guides kicking about on the net for this so I won't go into any detail here.
8. Cut the upper cowl grommet with a knife to remove it - be very careful not to nick and of the wires, particularly the ABS sensor.
9. Basically you now want the headlight wiring (10 wires) and bonnet latch sensor (2 wires) to run towards the wing and through a hole already present just to the left of where the bonnet release cable enters the cabin (looks like a bicycle brake cable going into a grommet almost vertically).
***The headlight wiring will need cutting as the 10-pin plug does not fit through the hole and even if it did I think you'd end up about 150mm short of wire to properly hide it away. The bonnet latch sensor wiring is really long for some reason so just slide that through and along the inside of the wing to where it needs to be.
10. Label up the 10 wires so when you cut them you know what joins to what. Sounds daft, especially as the colour coding is a dead give away, but there are two plain yellow and three brown (IIRC sat at the PC) and you don't want to mix these up. I opted for electrical tape and a sharpie and made two little "flags" on each wire with A, B, C etc. I then cut between the flags so A would join to A and so on. I left about 300mm of wire from the headlight plug before the cut so any joins would sit in the inner wing, not in the engine bay.
11. Double check when it's cut you know what joins to what then take a deep breath and snip away!
12. Take the headlight end which now isn't attached to the car to a bench and strip about 10mm of sheathing off each. Cut 10 extension wires off a reel of automotive wire. I used 1.5mm2 wire and made the extensions 200mm in length. I went for plain black sheathing for the new wire as I knew what was joining what and also it's going to be hidden away in any event.
13. Using all-in-one heatshrink/solder connectors attach an extension wire to each wire on the headlight plug.
14. Back at the car, feed the 10 wires for the headlight through the hole in the wing and out the arch of your car (between the tyre and the arch worked for me. Then get your newly extended headlight plug loom and do the same to connect all 10 wires back to the harness matching the little flags as you go.
15. Run it through the big hole in the inner wing where the washer bottle used to sit and plug it in. Don't worry about being neat at this point, you just want to test everything still works
Key in ignition and then cycle through the various headlight/foglight/indicator functions to make sure all your connections are good.
16. I guess you can do what you want at this point but I've opted for some self-amalgamating tape around the bunch of connectors to doubly seal them against moisture, and the OEM style Tesa harness tape (furry black fabric stuff) to protect and pull everything nice and tight together. I'd also recommend putting so corrugated split tubing around potential rub/chafe points.
17. For the brake fluid level sensor you could simply cut the connector and twist the wires together, but I quite like having the functionality - odd that, given its a safety critical system! Simply cut the connector and extend the wires by about 100mm, then feed it down the hole behind the little bracket thingy (?!) that connects the scuttle panel to the strut tower directly below the grommet. This doesn't fully hide the wire but neatens it up a little.
18. As above, you can do the same for the coolant level sensor, but again I like to have the functionality and visibility the coolant ball gives of the coolant levels, hence why I'm not deleting it currently. I extended the wires and ran it down the same hole as the brake fluid level sensor then hid it underneath the coolant ball and up into one of the little clips that sit on the "equator"lip of the coolant ball.
19. ABS Sensor - pushed this back through the grommet in the wheel arch and then re-routed it through the same hole as described in steps 17 & 18 above. No cutting required.
20. I stripped the wiring harness back from between the brake fluid reservoir and the strut tower back to the lower grommet in the cowl panel. This was to expose and pull back the two EVAP system wires into the cowl panel area. I decided to leave the exhaust sensors well alone for the sake of seeing a very short length of hose at the bulkhead get hidden. I wasn't down with cutting holes in the bottom of the scuttle/cowl panel.
Minor update, and it will coincide with another "Phase" of the wire tuck but the MAP pressure sensor wire annoyingly runs from the injector wiring loom and across the front of the engine between the block and the inlet manifold hose (just behind the drivers side headlight). I can't recall what the OEM position of the MAP sensor was as I have a FMIC fitted and the MAP sensor mounts on the hard pipe that sits down behind the corner of the bumper. The plan here is that when I unwrap the injector harness all the way back to the cowl panel behind the battery I should be able to simply route these wires along the cowl and through the same hole where I've sent the RH headlight loom and bonnet latch sensor above. Hopefully it will be long enough as-is but if not I can extend I guess.
*** I looked into this at the weekend and it's a major headache to strip the entire engine loom back for this one sensor. Once the injector/engine sensor loom is de-cluttered I'm happy to run this underneath the throttle body and behnd the inlet manifold turbo hose then tuck it above the headlight. Not strictly "tucked" but hidden well enough from view for the sake of the hassle.
Looking to get some more progress on it this weekend and finish the driver side them move onto the injector loom.
