Roverlike

Well, if you do not have that sensor I even more cannot see how your problem could be temperature connected.

Only in case we will make hypotesis that spring in your boot switch was in such state that it could or could not make connection and because of temperature changes, metal was contracting and expanding. Since spring is bare metal, in such case, hypoteticaly, it could make contact when it was not expected.

In above caee, when you corrected the spring in switch you solved the problem.

However, I cannot remember if you had one time more after you corrected spring, when alarm went off during a day? In that case above is questionable.

It is true that not all cars have microwave sensor. However it is easy to check if you have it or not. Leave door window in down position, close the car with fob and let few moments to pas. After that wave by your hand several times. If alarm goes off, then you have sensor, if not, then most probably you do not have it.

There are two boot switches. The one on which you made correction of the spring (let us call it boot lamp switch) and boot lock switch.
On both switches you have two (2) wires. Boot lamp switch have two single wire connectors going onto it. Boot lock switch have two wire connector. Take a look at picture I provided earlier on this thread.
Feed mentioned above is nothing else then earth wire from same position in the car as for door switch. This feed does not come from alarm, but from earth connection. Return wire is the one that goes to alarm. Black wire is earth feed and return wire is couloured one.

In case of mk1 MG F cars earth feed for boot lamp switch comes from another earth point then door and boot lock switch.
In case of mk2 MG F and MG TF cars earth feed for boot lamp switch and boot lock switch comes from same earth point connection.

Thank you for your feedback. Glad you sorted things!

Hogweed wrote:
Ummm… that little connector… so can I just disconnect the microwave sensor with that?

Yes, you can. Disconnect the plug and sensor will be inoperable. Then you could lock the car wirh fob and sensor will still be inoperable.

Hogweed wrote: OK, modified approach… I took the car out today for a good thrash, couple of hours, fast, slow, stop, start, open the boot/close it again, over bumpy roads etc, and no sign of the boot warning light coming on, so I cautiously suspect my diagnosis of a bent spring contact in the boot lock, which I absent-mindedly straightened again, was the cause of the warning light coming on.

You well may be correct as straightening spring might do what was needed. I assumed that you fixed that problem when you described earlier what you did.

Hogweed wrote: However, during the period when I isolated the switch completely, the alarm still went off once, so I suspect two problems. The car only has 14000 miles on it, so I’m going to take the view at this stage that the volumetric sensors are more likely to be responsible than the door switches – so will lock it with the key every night, and pray for the neighbours.

I was not aware that you did not lock only by key when you were trying things. I assumed that you isolated volumetric sensor during testing pwriod. If you did not, then, as you said, I would also suggest to do so and see if that is the problem, before attempting to do anything on door side.

Hogweed wrote: Just one thing… where are these sensors? Can’t spot them anywhere…

Sensor (you have only one) cannot be seen. It is microwave sensor (not ultrasonic one) and it resides on the (under it) T-bar in the middle of two seats.

Hogweed wrote:
Oh great. As Basil Fawlty said “I’m so happy.”

I am glad you are happy

Hogweed wrote: Does this micro-switch also operate the internal light when the door opens…?

In other words, do I need it at all…

Yes, these switches operate internal light when the door opens. If you want to isolate them, I can provide you info which pins you would need to isolate from door lock connector. However, in that case internal lights will never be on with door opening, and alarm will assume doors are always closed.

Hogweed wrote:
PS as it seems this is a common fault on TFs, if I buy a 2nd hand lock, is there not a fair chance it will be faulty too, or will go that way in the near future...?

That is true. It is a game of numbers and luck ...

Hogweed wrote:
Yeah, I’ve seen pictures – looks a beautiful place

Hhmmm, I’ll have a good look when the weather improves… but surely, the brake light wires wouldn't connect to the lock? And maybe I’m wrong, but I didn’t think the boot had central locking…

Yes, it is beautiful. Thanks!

For the wires, you are correct, brake light wires do not connect to the lock, but are passing around, that is the reason why I mentioned them. There you also have 2 wires for boot lamp. That would be 8 altogether.



2 single wire connectors would be C0107 and C0110 which are boot switch connectors and 1 double wire connector wou,d be C0831 which is boot lock connector.

Boot do not have central locking in sense there is motor which locks the boot, but is part of central locking system. Within boot lock you have switch which is part of central locking system in whole.

C1446 would be connector to actuator (motor) for central door locking system if you would have one, but you most probably do not have it. That is part which is mostly retrofitted on these cars.