Ive only had the car about 3 weeks but I cannot stand having dangling cables around and deep dashboard in the ST makes it difficult to get cables to reach. Based on previous posts regarding hardwiring road angels (credit to daviddabs) I had a crack at it this afternoon and took some photos on my phone along the way...
You will need:
A 12V ciggy lighter socket About 99p from ebay
<1m of wire. About £1.25 from ebay for 2m.
Fuse holder and fuse (this is optional - I didn't need it as my garmin plug has a fuse built in, but I would advise having a fuse in somewhere along the line)
Soldering iron and solder
10mm socket for earth bolt
Torch and a flat blade screwdriver for poking wires through and finding clips on the panels
1. Remove panel under light switch - held on by one torx screw beside diagnostic port in the recess. There are several spring clips and the door seal doing the rest of the holding. Be gentle and use a flat blade screwdriver for a bit of extra persuasion.
2. The panel comes off as shown below. The diagnostic plug is held into the panel using two metal spring clips, these can be held back to allow the plug to be removed. This will keep the panel out of your way.
3. The cigarette lighter needs to be connected between a switched live and an earthing point so that that the accessory won't be draining the battery while the ignition is off. I couldn't find the big yellow ignition wire the daviddabs mentioned so I decided to tap into the switched live for the light switch. Removing the light switch assembly gives better access to the connector behind it. It is removed by squeezing the two big tabs at the back together and pulling the assembly out from the dashboard.
4. The wire colours don't make it intuitive to find a switched live. So I had to spend some time with the multimeter and switching the ignition on and off to find a suitable wire. I found the red/green one, on the top row, second from left to fit the bill. However this may be different for other model years. Double check by placing a multimeter between it and an earth (like the inside of the front cigarette lighter). Meter should read 12V when ignition is on, 0V when ignition is off.
5. Shave off a small section of the cable coating and solder on the live cable of the socket you wish to fit. Be sure to wrap up the joint well with good tape and also put a cable tie around both wires to prevent stress on the joint when everythings back together.
6. Attach earth cable to suitable earth. The earth bolt I picked is below door hinge level on the pillar. The bolt itself has a washer which cannot be slid off. The washer only make contact with the part below around its outer ring so the only place for the wire to be clamped in place is between the bolt head and the washer. This means that a crimped-on eyelet connector will not work. I simply curved the wire to be a tight fit on the bolt, then soldered it to maintain that shape.
7. The photo below shows the earth wire in place. The trim in front of this bolt is held on by one clip fastener on the footwell side and the door seal on the door side.
8. Soldering on the socket to the other ends of these wires and doing a bit of tidying results in this:
9. I plugged in the satnav cable and taped it to the socket to prevent it working loose. I then turned on the ignition to make sure the charging light was coming on, indicating it was connected properly. I cabled tied the excess cable in a bundle and cable tied the entire bundle in two places to prevent movement or noise over bumps etc.
10. Routing the cable up to the side of the dash is awkward to say the least. but with a bit of patience and strategic poking it can be done. I ran the FM traffic receiver up the A pillar by taking the door seal off.
11. Now just put the main trim panels back on again, taking care to line up clips and not to snag any wires. Start the engine and make sure all lights and your satnav cable all work.
As you can see it was starting to get well dark and cold towards the end so I apologise for the photo quality. But hopefully it gives you some idea of what to expect. Done in around 2hours, a quarter of which was devoted to finding the right live wire. Any further questions give me a shout. And Mods - feel free to stick this in the How-To section.