Boot Lock/unlock mod on Central Locking, 85 Series3 Sovereign

Hi, I was reading here somewhere that there is a mod that can be done that allows the central locking to lock and unlock from the drivers door. At present my boot will only lock from the drivers door but to unlock it I need to go to the boot and use the key. I think this is normal for my car which is a 85 Series3 Sovereign. I am currently swapping out my boot lid for one that has much better paint and thought this would be the perfect time to implement the mod. Can anyone point me to the info needed to do it?

There may be one or wo steps, depending on what lock system you have, Kiekert or Lucas. Since 1985 was a transition year for the lock systems your car could be either.

In either case you’ll have to modify the actuating movement of the linkage at the lock itself. What I’m about to describe is very apparent on simple visual examination of the linkage, so don’t worry.

You’ll see that the linkage is deigned to actuate the lock in just one direction (frankly, I can’t remember if it is ‘push’ or ‘pull’). The linkage rests in an elongated slot so that movement in one direction actually operates the lock while movement in the other direction results in wasted motion. This wasted motion is what prevents the ‘unlock’ function.

The modification is simple: use a small bolt and nut…very small…to capture the linkage in the elongated slot. This eliminates the wasted motion.

On my '87 Series III this was all that was needed to complete the modification. That car had Kiekert lock motors, and the motor in the trunk was wired to operate in both directions, in unison with the motors at the doors.

My '85 has the Lucas system which uses solenoids instead of motors. The solenoid in the trunk was wired to operate in only one direction (again, I can’t remember if it is push or pull). It must operate in both directions to give both the lock and unlock functions.

Changing the wiring was fairly simple. The connector at the trunk solenoid has two wires but only one of them is used. The unused wire must be extended into the cabin and tapped into the wiring for the door solenoids, allowing the solenoid in the trunk to work in both directions in unison with the door solenoids. I recall this splice was easy to make at the bottom of the B-pillar after removing some trim…the exact details of which I can’t recall at the moment.

To determine which system you have simply follow the linkage from the trunk lock. If it attaches to a cylindrical solenoid, you have the Lucas solenoid system. If it attaches to a flat, square-ish box, you have the Kiekert motorized system.


Have you downloaded JAGCARE III yet from Jag-Lovers (it is free)? This excellent document, written by Dr. Gregory Andrachuk, covers lots of details about the Series III XJ6s and XJ12s that is difficult to find elsewhere. The details of how the boot lid locks work and how to modify them can be found on page 14.


Hi Doug I have the Keikert system so it looks like I got lucky there. Paul I have got Jagcare 111 but could not find the info you have referred to. I’ll go back and have another look now that I have a page reference.
Thank you both for the info

I merely use the key to lock and unlock??? Were it to pop open when un locked from the cabin, I might have been tempted, at one time…

Although my Jeep’s really heavy hatch can be unlocked or locked from the cabin, it would be neat, if it lifted as well.

As I recall Doug had a hand in the production of Gregory’s excellent treatise, Jagcare III… Enjoyable and informative reading…

Cold and wet around these parts. More hibernation…


Since I’ve owned my cars, 86 & 87 series 3 XJ6’s, I had to have the Kiekert locks on both cars. What’s interesting is, over the past year, the locks on both cars, modified for the solenoids to lock and unlock the boot lids, now seem to operate in an intermittent manner, meaning sometimes unlocking the driver door will operate them, sometimes not. If I use the key to lock and unlock the driver door several times, eventually, I can hear the sound of the locks opening or closing in the trunk as they are supposed to do. Strange this phenomenon has begun right around the same time for both cars.

MRCHB, an easy place to start is to remove the door trims and simply lubricate the linkage rods. This often solves erratic operation of the locks

I’ve also found it helpful thoroughly clean the actual latch mechanisms. Use a spray solvent of your choice to remove dirt and elderly, hardened grease. Then spray with a light lubricant of your choice


Not really. I recall helping with some pics but the content is all Gregory !


Is the erratic operation confined to the boot - or affect all doors…?

If the former; check Kiekert and linkages at the boot - if the latter; the control unit may be out of adjustment.

As the key is turned; one rod unlocks the driver’s door, another rod moves the control unit - which triggers a short power pulse of relevant polarity to turn all the Kiekert motors to lock/unlock…

Functioning correctly; all motors, including the boot, react to each key turning - but the ‘slip’ joint on the boot linkages prevents unlocking.

As Doug says; cleaning and lubricating is certainly relevant, but simultaneous failure of all locks to react each time the key is turned, implies a control unit issue…

As an aside; you should verify if all doors are locked or unlocked if malfunctions occur - to locate individual faults…

xj6 85 Sov Europe (UK/NZ)