Our 500c is coming up for five years old. When it was about a year old the wires between the body and the boot/trunk lid started failing so the dealer replaced the whole car loom under warranty.

But it started to fail again three years later, this time out of warranty. The boot release handle stopped working (although the keyfob release still worked) and then last week the numberplate lights stopped working. The dealer offered to fit a new loom for around £700 and also warned me that auto electricians are aware of the OEM fix cost and consequently charge an arm and a leg for a repair (which is probably not true, but I haven't checked).

I thought I'd try and fix it myself before seeking help. And I did it this morning. Took about two hours and cost me about £6 in materials (wires, chocolate blocks, heat-shrink tubing).

Here's what I did.

1. Disconnected the battery.



2. Removed the trim panel from the boot itself. There are 8 black plastic push-fit rivets that can be levered out.



3. Removed the trim panel from the top of the boot, under the "parcel shelf". Another 8 of the black plastic rivets.


(Looking upwards at the bottom of the parcel shelf.)

4. I completely cut the wiring loom where it had started to fail, and disconnected the two electrical connectors in the boot lid. You can pull the cut end with the rubber strain-relief back through the body hole so it hangs free from under the parcel shelf to give more slack.



5. I used chocolate block connectors to join new lengths of wire to the seven wires in the factory loom. Auto electricians and experts will probably recommend soldered joints, but I assume the new wiring will fail again in the future and I want to be able to fit new replacement wiring again easily if it does. I hope these terminal blocks will be OK?

The wire I added between the two cut ends was 50cm long, which was just about the perfect length, allowing room to install the chocolate block terminals and a longer length exposed at the boot hinge. Maplin sell 7-core trailer lighting wire with a black sheath that would have been perfect, but were out of stock yesterday so I bought standard automotive wiring and used seven lengths. I don't know how flexible the trailer wiring would have been.



Since I used separate wires I added heat-shrink tubing to protect the wires in the hinge and make it look as OEM as possible.





6. The hardest part of the job was getting the new wires through the rubber strain-relief boots so that the boots could slide over the wires.



I found a plastic Calpol syringe that was the perfect size for the wires to pass through. With a bit of silicone spray to lubricate it I was able to push the tube through the tight rubber boot, then slide the wires easily inside the tube. Pulling the tube out left the rubber gripping the wires.



Job done.



Same at the other end.



I've allowed about 20cm of visible wire between the tips of the strain-relief boots, which is about 7cm more than the factory loom allowed. The wire loops really comfortably now when the boot lid is closed, so I hope there won't be any further pinch-points.

7. More chocolate block terminals at the other end and it's all back together.



The boot release button now works again and so do the numberplate lights. How satisfying.

Thanks heaps for your post, but can you please upload the images to the forum rather than linking them? All of the googleusercontent hosted images are broken and don't show up.

I've always thought that chocolate blocks are considered totally unsuitable for cars (due to vibration?). Have a feeling I read it in a kit car building book years back but it's a foggy memory.

In theory, you should be good to solder the wires as if it's the same root cause as the tin-top hatchback cable issues the problems are caused by the wires being too short, which you seem to have rectified?

Images also broken here.

Chocolate Blocks connectors are fine if you solder the tails first and use the correct size block for the cables. TBH, I would consider them if and when I have to do ours.

The good thing about using them, is that you can repair it again and again with relative ease.

Yes, the photos are un-get-at-able here too.

Thanks,
Mick.

Balls - thanks for letting me know about the pictures. Apparently I can't edit the original post any more so I'll create a new one with Photobucket pictures instead, and alert the mods.

Our 500c is coming up for five years old. When it was about a year old the wires between the body and the boot/trunk lid started failing so the dealer replaced the whole car loom under warranty.

But it started to fail again three years later, this time out of warranty. The boot release handle stopped working (although the keyfob release still worked) and then last week the numberplate lights stopped working. The dealer offered to fit a new loom for around £700 and also warned me that auto electricians are aware of the OEM fix cost and consequently charge an arm and a leg for a repair (which is probably not true, but I haven't checked).

I thought I'd try and fix it myself before seeking help. And I did it this morning. Took about two hours and cost me about £6 in materials (wires, chocolate blocks, heat-shrink tubing).

Here's what I did.

1. Disconnected the battery.



2. Removed the trim panel from the boot itself. There are 8 black plastic push-fit rivets that can be levered out.



3. Removed the trim panel from the top of the boot, under the "parcel shelf". Another 8 of the black plastic rivets.


(Looking upwards at the bottom of the parcel shelf.)

4. I completely cut the wiring loom where it had started to fail, and disconnected the two electrical connectors in the boot lid. You can pull the cut end with the rubber strain-relief back through the body hole so it hangs free from under the parcel shelf to give more slack.



5. I used chocolate block connectors to join new lengths of wire to the seven wires in the factory loom. Auto electricians and experts will probably recommend soldered joints, but I assume the new wiring will fail again in the future and I want to be able to fit new replacement wiring again easily if it does. I hope these terminal blocks will be OK?

The wire I added between the two cut ends was 50cm long, which was just about the perfect length, allowing room to install the chocolate block terminals and a longer length exposed at the boot hinge. Maplin sell 7-core trailer lighting wire with a black sheath that would have been perfect, but were out of stock yesterday so I bought standard automotive wiring and used seven lengths. I don't know how flexible the trailer wiring would have been.



Since I used separate wires I added heat-shrink tubing to protect the wires in the hinge and make it look as OEM as possible.





6. The hardest part of the job was getting the new wires through the rubber strain-relief boots so that the boots could slide over the wires.



I found a plastic Calpol syringe that was the perfect size for the wires to pass through. With a bit of silicone spray to lubricate it I was able to push the tube through the tight rubber boot, then slide the wires easily inside the tube. Pulling the tube out left the rubber gripping the wires.



Job done.



Same at the other end.



I've allowed about 20cm of visible wire between the tips of the strain-relief boots, which is about 7cm more than the factory loom allowed. The wire loops really comfortably now when the boot lid is closed, so I hope there won't be any further pinch-points.

7. More chocolate block terminals at the other end and it's all back together.



The boot release button now works again and so do the numberplate lights. How satisfying.

zanes said:

I've always thought that chocolate blocks are considered totally unsuitable for cars (due to vibration?).

Click to expand...

Mick F said:

Chocolate Blocks connectors are fine if you solder the tails first and use the correct size block for the cables. TBH, I would consider them if and when I have to do ours.

Click to expand...

I must admit, I did wonder about the suitability of chocolate block terminals for this but we'll see how we get on. I don't like crimped connectors for tiny little CANBUS signal wires and didn't think of a better alternative. If the chocolate blocks vibrate loose I'll get my soldering iron out. Thanks for the warnings.

Anyone performing a similar repair should consider using silicone wire. It has many more thin strands, which together with the silicone sheath makes it very flexible. It's available from r/c model suppliers, such as here:
http://www.hobbyking.com/hobbyking/store/__466__377__Hardware_Accessories-Silicon_Wire.html

Thank you very much SiliconS for this. My wife has a '13 plate 500C and last Monday the number plate warning light came on plus the boot would only open on the key fob. The Calpol syringe saved a. Assigns amount of time vs just pushing with silicon spray...

I followed the instructions above and it is now working again.

A few bits that might help:

- I used 7-core trailer cable from Halfords - for only a tenner worked perfectly. It has a robust outer.
- I stripped and tinned the ends as per the guidance. I also used choc blocks.
- The plunger from the calpol syringe worked well to guide the syringe tube through. Once cut, the tube has rough edges, so the plunger prevents damage to the grommet.
- wrap the finished article in self-amalgamating tape (4 quid from Screwfix) to prevent sticky residue and ensure water resistance.

- key didn't open or lock afterwards for a few mins. Must take some time to sync back to the car.

Yossarian

You're lucky, the hatch back has upwards of 16+ wires, if using the correct type of cable its unlikely to ever fail again in the cars life too.
I too had the non opening of the boot at first for a few mins( a Oh no now what moment ) so guess this is normal.

This is just happening to oh car now....bloooming ref plate light not working...can see a broken wire
2012 500c

So i spent some considerable amount of time doing this on Saturday. Almost all of it trying to get wires through the gromits....It really is unnecessarily difficult!

Crikey.. hosted photos that still work

They must have 'paid the ransom'