Fine work, Mike, posting these up gives us a good idea of whats inside, the switch bank looks quite robust and really, the lock motor should work forever and a day, its just the plastic gears and sliders, work of the devil!
I think I found in mine that the root cause of the issue was the worn plastic bush in the key barrel lever, stopping one of the rods to pull the switch properly, hence the machine gun rattle of the locking motor.
This may be a common problem and would be the first thing I will now check with a faulty locking unit.
NC is normally closed and NO is normally open, if you look at the diagram, you can see the switch configuration.
I have not stripped the switch down, so not sure exactly how the swiches are laid out inside the unit, the info I had were taken from the bench test I did on mine when it was out of the vehicle. For instance, the signal for the locked switch on pin 3 changes state when you operate the mechanical latch simulating closing the door.
Although I have stated N/O and N/C for the lock switches, this is referenced from the drawings and I am not sure if this is in regards to the door open and unlocked or closed and locked. This would also be good to know.
It would be worth while, if stripping your lock down to see if there are any problems inside, to post up some pictures of the unit in pieces and what switch does exactly what and where inside it is situated.
I would certainly have done that if I had pulled mine to bits, but knowing how tricky they can be to put back together (been there and done that with my ZT) I was glad I did not have to.
The electrical schematics I have are the ones taken off this site in the download section, they were drafted or issued in August 2003 (about right for me, as my car was assembled in Dec 2003 and registered in 2004. So far I have done quite a bit on the electrics and not found any errors in the schematics and what is on my car.
I actually applaud the designers of the electrics on our cars as the schematics are easy to follow, well labelled and cross referenced. Probably the best auto electrical schematics I have ever used!
It does help being an industrial electrician and having electrical control system design experience though.
Good luck with the fault finding, and keep us up to date, maybe after you get this sorted and acquire more data, we could possibly write up a detailed how to for diagnosing and repairing these locks between us, even if its just a set of expected reading when certain switch are operated.
Rick Buhllar is quite well known in most of the MGF / TF facebook sites, and is the guy who sells a lot of custom illuminairs for our cars, he is the guy who does the Halo headlights conversions for the TF and also does the progressive indicator mods.
I bought some illuminated kick trims from him and they are really good.
Some may not like facebook, but there are a hell of a lot for our cars on it, including at least 4 MGF and TF groups including modified groups, local groups and sales pages.
I also use it for my Meccano hobby, and shooting hobby to. Anything you don't want you just block.
For anyone who may find it useful, here is a scan of the MG-Rover drawing for the door lock, and followed buy a map of the pinout of the connectors for the lock unit ( as seen on the lock itself, not the wiring harness).
Look for a resistance of about 1 ohm on the switches (3 to 4 ohms with meter lead resistance) and between 17 and 30 ohms across the locking motors (I cant remember which was which).
I definitely had a door rattle but not driven the car since fixing it earlier. Now I find that some old biddy visiting next door has scuffed my bumper! just 4 weeks after having it resprayed !
