Locked out and will not start - alarm sounds off

Electronic experience required please.

The basics  A 2003 MGTF 135 with Lucas system.
The problem Engine will not start - and in the short term that’s all I need. So I can get the car in the garage.

Background
About a month ago the drivers door handle broke off. This was repaired by replacing it with a spare used component.
After re assembling the door furniture etc there was a moment of “Clickety clack” with some but not full movement of the door lock button. After a couple of operations with the fob and opening and closing the door it all settled down.

Unless a mistake is made the door is always locked using the key and not the fob. As far as Im aware this does not utilise the dreaded super lock.

Went to unlock the car today as normal by using the fob for that purpose. The passenger door unlocked ok but not the driver’s door. Operation of the key in the lock should override that condition but it didn’t. So facing the possibility of destroying the trim we tried a few things and eventually with my ever willing glamorous assistant grabbing the button as reached its max travel and pulling it further up whilst I operated the door handle and key in the lock we managed to get the door open.

The trim panel was removed and door lock mechanism removed and re connected electrically we tried to start the engine but no luck.
Things got a bit mixed up after that but we had alarms sounding, the electronic box of tricks hidden behind the carpet under the dash in front of the door hinge chattering away to itself at around one click a second. 

With a second door mechanism connected in place of the one just removed it made no difference i.e. chattering from the electronic  box of tricks , horn sounding if trying to start the engine.

I really need some expert help on this please!

Have you tried disconnecting the door lock again to see if the chattering stops

This is not normal behaviour. My first tought is that you either have earth broken somwhere or wires in the boot broken, or both.

I would first try to disconnect what you were last working on, the door loom and see will that help anything.

Thank you both for your responses. 
I agree it is not normal and Im way out of my depth with this.
As I sat down and thought about it over dinner I have perhaps made an assumption. When the unsighted ECU was chattering I was unable to pinpoint it exactly and whilst standing outside the car it appeared to come from the control unit i described. But perhaps it came from the red coloured control unit located behind the fuse panel. Would that make any more sense?

With the lock fully disconnected mechanically and then electrically the same results occurred i.e. no engine start and sometimes but not every time the alarm going off requiring the blipper to be pressed to silence it.

I had two other lock mechanisms one that gave me the full “machine gun” rattle some 3 years or more ago and the item I have just removed fixed that.
The second spare (until now untested and unused by my) was fitted to the loom but not the door to see if it needed micro switch contacts to provide continuity to the ECU . But thinking about that why would it thecengine should start whether the door is open or shut. But this made no difference the result was the same. No engine start. 
I probably tried with the door mechanism tricked to thinking that it was shut to reduce battery drain. I did this by pushing the latch shut with a small metal object.
The other ECU unit I have subsequently thought about is the YWC104500 Red Multifunction Control Unit MGF MG TF Rover Lucas .
Im trying to see what this might control.

Does any of this make any sense?

 

Let’s think about the relay operating in the footwell. Does your car have one shot windows, I suspect the answer to this will be yes. The controller for this operation is in the drivers footwell, behind the carpet & just in front of the hinge. This functions by taking a signal from a monetary “jab” at the window switch, the system latches on, dropping the window, until a pre proscribed amount of current is drawn by the increasing amount of work done by the motor. The system then resets for its next operation.
This box of tricks should not be doing anything in its quiescent state, this network requires investigating, if the relay is operating.
M

Regarding window operation. I’ve never stopped to think what they do or don’t do. I press the button, hold it, and they go all the way down. I’m fairly sure that if I release part way down (or up) they stop.

As you might imagine I have tried to establish what these modules do. For clarity the red one appears to have a test feature.
This apparently can test the locks. I don’t know what feature it tests but it does seem to be too much of a coincidence.

From what I have read the test is initiated via the hazard switch in some way but that has not been initiated since the MOT in March at least not by intention. Climbing across the car to get out the passenger side might have brushed it but that would have been with the key out.

And the issues i described were repeated without any further action other than trying to start the engine.

So if anyone can think how the issue I described in my first post can be linked to this “red module” without initiating a test I like to know please.

Can you describe what happens when you try to start the engine - any sound, anything, or you just turn the key and nothing happens? What is the status of lights on the dash - do they glow withouth problems, not dimmed?

Alarm should not go off and start the horn sounding unless car is fully locked. So that should not happen while you are trying to start the engine. 

How you can set alarm to armed state? By lock on drivers door. That would mean you need to inspect wiring from drivers door to inside the car to see if you have wires broken and touching something. Continuity testing would be my suggestion.

When attempting to start the engine the panel lights dimmed.

From what I can recall from yesterday afternoon the horn might not have sounded every time I tried to start the engine before I removed the door lock, after I removed the door lock, or after I swapped it out for a spare. The rapid switching in the control module developed during the afternoon i.e. at first that didn’t occur but my recollection is that it happened more often if not every time I tried before I gave up.

The battery was disconnected when I finished work on the car yesterday and has been on trickle charge overnight and later today I’ll see if that made any difference.

I can check for continuity if I knew where to check. Do you mean connect the multi meter between each of the pins in the door lock loom socket to “ground”? 
At least one should be open circuit.
Do you have reference to the loom colours that should go to ground in the “unlocked state” with the battery disconnected please?
Clearly to do that test with the battery connected must risk “shorting to ground”

With the battery connected my expectation would be that I could test relevant pins to earth with the meter set to read 12 volts.

Otherwise which continuity test do you suggest please?

Continuity testing means you are testing to see if the wire is not broken not if it has voltage.
If say you have a red wire at the lock then through the wiring diagrams find out where it runs to. Then with the meter set to Ohms put the probes one on each end. You should have a resistance reading in ohms and not OL..which means there is no continuity.

I have been reluctant to post this next part because I don't wish to cloud the issue.

When I got my car occasionally I would open the door with the Fob, get in and turn the key and the alarm would go off and it wouldn't start. I had to disconnect the battery to stop it and start again.
On this forum AP pointed out the boot hinge wiring problem and also the micro switch on the boot lid.
The loom was perfect but the microswitch was stuck confusing the alarm.
A quick clean with Deoxit and it has been fine ever since.
The unpredictability of it going off was driving me crazy not to say it was embarassing too.
You could have a similar microswitch problem in your doors.
Best of luck.

From a “Roverlike Post” some months ago I have come across the following.

6-way plug:
Pin 1: Lock motor direction wire 1 Orange wire 
Pin 2: Drivers door open microswitch Brown/Red wire (microswitch 2) - used in cojunction with boot swith tied with microswitch 1
Pin 3: Sill down from microswitch Black/Pink wire (microswitch 1)
Pin 4: Lock/Superlock motor direction wire 2 Pink wire
Pin 5: Superlock motor wire Brown/Pink wire
Pin 6: Drivers door open microswitch Pink/Grey wire (microswitch 3)

2-way plug
Pin 1: Sill up from microswitch Black/Orange wire (microswitch 1)
Pin 2: Ground/Earth Black wire

All these wires (except ground wire) goes directly to 5AS, or they come from 5AS respectively.
What I would do is use a multimeter and check which microswitch provides signal to which wire and under which case. 
End of Roverlike post.

So to continue :~ from this I can see a relationship to the boot switch and wiring in the boot. As there is a relationship with the bonnet switch and the alarm (where some suggest decreasing battery voltage also enters the equation) shouldn’t there also be a relationship between door button and bonnet switch?

Can anyone add more to this please?
 

Would a PScan help matters? I was kindly lent one by a member and it pointed out the fault immediately.   Even if I, initially, did not understand what it meant! 

In this instance I don’t believe Pscan could help, but I’d be happy to be proven wrong. I do have one of those .

After fumbling around in my spares box I have located a spare “red” control unit and could fit that if it was thought to be at fault. However access to it I believe is difficult and requires the major fuse panel to be “dropped” out of the way.
Has anyone done that and if so how difficult is that to do without making matters worse.