MG F/TF Boot Hinge/Lid Wiring Loom Inspection Guide

Due to opening and closing of the boot lid, wiring loom attached to boot lid is folding every time. This folding can eventually lead to breaking of wires within this loom. This breakage can lead to various type of problems from non-operating third brake light to alarm sounding during night.








It is wise to make inspection of this loom in order to see if you have broken wires and you need to repair them.

When repairing them, it is wise to make them tad longer then before, as this will allow more easily folding space thus making breaking less likely to occure next time.

Following is list of wires that are passing to boot lid, for you to be able to identify them.


MG F/TF Boot Hinge Wire Colours & Functions:
_____________________________________________________

Mk1 MG F has 8 wires in this loom

Black ............................... 0,5 mm² - Boot Lid Switch - earth wire
Purple/Red .................... 0,5 mm² - Boot Lid Switch (when switch is closed this wire is earthed)

Black ............................... 0,5 mm² - Boot Lock Switch - earth wire
Black/Red ...................... 0,5 mm² - Boot Lock Switch (when switch is closed this wire is earthed)

Black ................................ 0,5 mm² - Third Brake Lamp - earth wire
Green/Purple ................ 0,5 mm² - Third Brake Lamp (when brake switch is closed this wire is live)

Purple .............................. 0,5 mm² - Boot Lamp - live wire
Purple/Red ..................... 0,5 mm² - Boot Lamp (when Boot Lid Switch is closed this wire is earthed)

NOTE: Purple/Red wires of Boot Lid Switch and Boot Lamp are joined in the loom within engine compartment when they pass from boot lid.

Mk2 MG F and MG TF have 7 wires in this loom

NOTE: Boot Lid Switch earth and Boot Lamp earth wires are joined in the Boot Lid






Note that if you have broken wires at folding area and among broken wires are earth wires of Boot Lid Switch (Load space switch) or Boot Lock Switch (Tail door open switch), since these earth wires are coming from the earth header joint from picture below, whole earth header is/might be compromised. This means that all circuits listed on the picture might not work. Since among them is Fuel tank unit, you might not be able to start the car.





If among broken wires is Third Brake Lamp (High mounted brake lamp) earth wire on following picture you see what other circuits are connected to same earth point, which will/might not work due to this break of the wire.







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Roverlike . Well done for this , very impressive .
John .

I found this thread very useful today and found that all my wires into the boot loom were broken, I am confident with these well written instructions that |I will be able to repair it easily, thanks 

It doesn’t matter how far down the track we are, posts like this from Roverlike are probably of greater value now than when originally posted.
I have frequently commented on spurious alarm soundings & there in the first paragraph comes the echo of those comments.
I thanked our friend then & I do so again now.
M

My 2005 had shorted and melted the wires in the boot lid. I made a new loom and all works except the light. One purple/red wire has 12V which I connected to the lid switch, the other purple/red has no volts and is open circuit both locked and unlocked. If I joint the two wires together I will have 12V on both sides of the bulb, is this correct. Thanks

BobPatchett wrote:

My 2005 had shorted and melted the wires in the boot lid. I made a new loom and all works except the light. One purple/red wire has 12V which I connected to the lid switch, the other purple/red has no volts and is open circuit both locked and unlocked. If I joint the two wires together I will have 12V on both sides of the bulb, is this correct. Thanks

NO, as you describe that is not correct.
First of all no purple/red wire should have 12 V (power). Only plain purple wire should have 12V.
Second you cannot have power connected to boot lid switch, that is wrong, since when boot lid switch is closed it will earth that wire and make short circuit. 
Third, you cannot connect as you mention to have 12V on both sides of boot light. One side must be 12V, above mentioned purple wire, and that is the ONLY powered wire among all, and the other side must be opened circuit, which is earthed when boot lid switch is closed (lid itself is opened).

As I see it you did not get it correct.

Thank you Roverlike for the guide, and in particular for detailing the wiring colours as this saved me from having to reference the wiring diagrams in RAVE.

I've been aware since I inherited our TF that opening the boot without first disarming the alarm with the fob would often trigger the alarm to sound, and also that even if I did unlock with the fob first, having the boot open did not prevent the car from locking again automatically after 30 seconds.

I've completed the repair this weekend, but taken a slightly different approach, so thought I would document what I have done in case it is of any use to others.

As is common, most of the damage to the existing wires, whether they were completely broken, or damaged but not yet severed, were very close to where they exit the main loom bundle. I first unwrapped the loom as far forward into the engine bay as I was able to reach without unbolting the engine cover, and back to the rear corner near the rear ligjht clusters as at least a couple of the wires run in this direction. I then cut the wires such that the new joints and their heatshrink would be contained entirely within the main loom once it was taped up again.

I then cut all the wires between where the hinge meets the bootlid, and the grommit where the cables enter the bootlid cavity - there are already factory crimps joining some of the wires in this area and it seemed a good place to make reliable joints that are easily accessible and replaceable in the future if needed.

 

To preserve the factor colour coding of wires, I used undamaged sections of the wires I cut out to extend those in the main loom so that they were long enough to exit the loom with in the same place as the wires going to the earth point below the boot hinge. I used uninsulated crimps and heatshrink for these joints, as this tends to be how factory joints in looms are made, but I see no issues with using solder and heatshrink instead given there will be no movement here.

 

I then terminated all of these extended wires into an 8 pin sealed automotive socket, and wrapped everything back up in Tesa (fabric loom) tape. It's not shown in my photos but I have also since 3d printed a clip to securely attach this connector to the existing hole in the adjacent metalwork. Since all of this cabling is now fixed and not exposed to constant movement every time the boot is opened or closed, I am hopeful I will never have to revisit this part of the wiring.

 

I then terminated 7 new wires into the mating plug (you would need 8 on an F), wrapped these in Tesa tape too, and put the existing split tubing over the top for good measure. I used 0.5mm² fine stranded silicone insulated wire for this, as it is much more flexible than the original pvc insulated wires, so will hopefully last longer. Having plugged this into the new socket on the loiom, I noticed there was an almost made to measure extrusion on the fuel filter bracket, so I placed the new cable bundle here and used a cable tie around the fuel filter to hold it in place, then left a small loop, and routed it up the hinge as it was originally. I then used more crimps and heatshrink to connect these new silicone wires to the exiting wires on the underside of the boot lid.

 
 

My reasoning for doing it this way is that the main loom, and the wires exiting from it are no longer subject to any movement - they simply run to a connector which is secured into place. The new silicone insulated wires should be more resistant to constant bending from opening and closing the boot, but even if they break, I can simply unplug the connector and replace them - I won't need to unwrap any of the main loom or try to make new joints in what is a bit of an awkward area. The only crimped joints I would need to make would be on the underside of the bootlid which is much easier to access. I did consider adding a second connector here, but decided that would be even more overkill than what I have already done!
 

Thats a great job and very well documented.
Thank you.

You have made an excellent job which will avoid future failures by improving on the original design.

Thats a 10/10 from me

Good right up, adding in those connectors will also make removing the boot a whole lot easier too.


Where did you get the conenctors from?

I bought a box of assorted deutsch type connectors from AliExpress a while ago, but the same connectors can also be found on Amazon and ebay:

https://www.amazon.co.uk/dp/B0FG23V2Z9/

Excellent methodology & a well chosen connector. I might crop my rather inferior “plug & socket“; connector being too grand a title & follow your example.
M