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MG MGF Technical - HELP - Alarm test from Mr Cadwell

Okay, I know the alarm test.

If I sit in my car and activate the test.
I open the drives door, the light flicks on.
I open the passenger door, the light flicks on.
I can't open the boot or bonnet without removing the key.
What do I do to test these?

I know there's a problem as the lights don't flahs when I lock the car.


Confused of Bucks!
Neil H

The bonnet is 'shut' to the alarm even if it is only 'on the latch' - which leaves the boot, where under further investigation you will find a few (broken wires/wires rubbing) at the hinge -

just call me physic ;-)

Will Munns

Alarm test? How do you do that?

Will.. - I can't see any fraid wires.. - that was my first peek!!
Any ideas how I can test.

Fred: - This is copyright of our resident expert Mr Bruce Cadwell: -

Alarm system test
The alarm system can be tested by following the procedure described below:
1. Ensure doors, bonnet and the boot lid are closed.
2. Sit in the driverís seat and close the door.
NOTE: The next three actions must be carried out within 2 seconds.
3. Depress the driverís doorsill button.
4. Switch the ignition on, off and on again.
5. Raise the driverís doorsill button.
If the test mode has been entered correctly, the horns will give a short beep and the engine immobilisation buzzer will sound.
Opening either door, the bonnet or the boot lid, or operating the driverís doorsill button, will cause the alarm LED to illuminate for approximately one second. If the LED does not illuminate, there is a system fault.
The volumetric sensor can also be tested while in test mode. To test the volumetric sensor, press the unlock button on the remote handset several times. The alarm LED will illuminate for approximately 1 second each time movement is detected in the vehicle.
Neil H

Neil, can you close the catch with a pen to check the light goes off?
Will Munns

Okay Will.
Good idea..
..Just tried and the light does go off.

With alarm test, the drivers door works, the passenger door works, the volumetric sensor picks me up when I move, and the boot light goes off when I close the catch with a pen.

What next??!?
Neil H

next is to lock the boot with a pen and see if the alarm will arm, if not then it could be a fault with the door sill detection (ie the alarm say 'lock' but doesn't get a 'im locked' signal back from the door)
Will Munns

Okay Will..,

Drivers door - ok
Passenger door - ok
Volumetric - ok

Open Boot
-Leaving the boot open I lock the boot with a pen and the boot light goes off.
-Now, leaving the boot open I lock the car with the fob. The indicators do NOT flash (they don't flash at the moment in normal operation either). The doors lock and after a period of time the alarm LED starts flashing.
- From here, I leave the car locked and alarmed with the boot open, but thinking its locked. Now I release the bonnet - nothing happens. Now I open the bonnet and the LED stops - if the horn was connected, I think I'd be getting a few noises now.

What's that mean then??
Neil H

>Now, leaving the boot open I lock the car with the fob. The indicators do NOT flash (they don't flash at the moment in normal operation either). The doors lock and after a period of time the alarm LED starts flashing.<

99% sure that is normal, or at least what my car does. I close doors, open boot, zap lock, put zapper in pocket, get wife's xmas pressie out of boot, shut boot and lights flash.

Also normal to open boot with key when alarm is set. BUT front bonnet triggers alarm when opened.

No.., that's not whats happening.

With the boot shut, if I lock the car, the indicators don't flash.

If I lock the car with the boot open, then indicators don't flash.

In fact, no matter what I do, the indicators don't flash when I alarm the car.

- yes, the indicatros do work whilst driving though :-)

Neil H

You got a spare key? Use this to test the boot.

Also, check the inside of the boot lock, there is a tiny microswitch here that tells the alarm ECU the boot is unlocked properly and not forced. I had a broken microswitch and the alarm would sound if the boot was opened - replaced the microswitch and it is working properly again now.
Scarlet Fever

Does it always default to alarmed if the boot is opened? Mine is the opposite.

Is it that wire thing on the inside of the latch (boot lid) itself?

Presumably, if I can trick the car into sending the right signals from this microswitch I could eliminate it from the tests?

So.. is touching the two wires together what I should do?

Neil H

From the description it would indicate (no pun intended!) that there is either a fault with the Alarm ECU itself or a fault with the wiring from the Alarm ECU which feeds the indicators during alarm setting and unsetting. The wire colours are Green/White and Green/Red. Green/White feeds the RH indicators and the Green/Red... you guessed.

Since both banks of indicators don't work, when setting the alarm, it would seem logical to suppose that the ECU is at fault because it is unlikely that both wires would fail at the same time. It is still worth checking them out to make sure that someone or thing has not cut through them. They are next to each other on the Alarm ECU pinout. Maybe the plug on the ECU is loose. The No 3 Fuse under the bonnet feeds the Alarm ECU and the indicator lights (when setting the alarm). This fuse is most certainly OK or the doors would not open using the blipper.

Hope this helps and let us know what it was, when you find it.

Bruce Caldwell

Oh, and PS, the name's Caldwell, not Cadwell but you can call me Bruce! The alarm test was first posted on this site by Spyros in Nicosia.

Bruce Caldwell

Ah! Mr Caldwell.. - I suppose the name error makes up for the days of loneliness from the BBS!

Sorry Sir!

I was thinking microswitch?
If the microswitch in the boot does not register that the boot is shut, then the indicators will never flash?
-- what'd'ya think?

Going with you theory though, this whole problem started when I took 2 bikes, 1 good lady, my small rucksack and her bags to Monte Carlo.. Hence the boot has probably had its fair share of packing.

Neil H

Find your spare key and check the operation of the alarm test again. Make sure that the LED flashes when you open the boot with the key. If not then the problem lies within the boot lock wiring. As Will says, it may well be the wiring going around the hinge. If a wire is open circuit then the system will assume the boot is open and the lights will not flash when you arm the alarm. A door or bonnet open will also stop the lights flashing when you arm the system. Disarming should make the lights flash once whatever.
Do your's flash once when you unlock?

Bruce Caldwell

I can't find the spares, as I moved house recently :-(

With the car locked with fob.., if I wait until the LED is flashing and open the boot, I don't think the car notices. The LED continues to flash.
Neil H

<<If a wire is open circuit then the system will assume the boot is open and the lights will not flash when you arm the alarm.>>

Should read

If a wire is SHORT circuit ie like the switch is made, then the system will assume the boot is open and the lights will not flash when you arm the alarm.

Bruce Caldwell

Can you repeat the alarm test procedure as described above (taken from the MGR Manual) but first leave the boot open. Push the catch over on the boot lid lock so that the system thinks the boot is shut. Use an old ballpen or something. Then set into test mode and get out and move the boot lid up and down to flex the wires at the hinge. If the problem lies there then it may show up as a flash on the LED. You really need to find/get another key.

Whereabouts in Bucks are you?

Bruce Caldwell

AND do your lights flash when you disarm the system with the blipper?

Bruce Caldwell

Okay, the lights DO flash when I disarm..

I will go outside into the car park now and retest, boot open.. etc.

Back in two.
Neil H

<<Okay, the lights DO flash when I disarm.. >>

This confirms that the ECU is OK.

Bruce Caldwell

Okay, Boot open, and latched with a ballpoint pen.

Alarm test sat.
Get out of the car, light flashes, and shut the drivers door.

Waggle the boot open and shut, nothing. Wave the wires on the left of boot hinge around as much as poss, nothing.

-- What happens if the microwitch is blown? Does the alarm assume the boot is open or closed?

-- Bucks - In Marlow.
Neil H

<<-- What happens if the microwitch is blown? >>

System assumes boot is shut all the time.

If you are sure that all the other apertures are working correctly then the problem must lie in the wiring in the boot. Have you tested the bonnet? And also, does the light come on in the boot when you open it normally? If not then a wire has come drift on the boot switch or lamp.

Bruce Caldwell

<<-- What happens if the microwitch is blown? >>

Remember, there are two switches in the boot. One for the lock and one for the key. The lock one operates the light in the boot and the key one tells the alarm to disregard the boot opening while the alarm is set. It assumes you have a key.

The problem can't be a wire fallen off from the switches (thinking aloud) otherwise the lights would flash when setting the alarm, so it must be something like the switch on the lock not mechanically operating at all or the key switch is closed all the time. If the boot light works then the lock switch is working and therefore it must be the key switch closed all the time.

Bruce Caldwell

With boot open, but car thinking its shut (ballpoint pen) ..
I can put the car into test mode.

If the bonnet is unlatched from the boot - nothing. If the bonnet is opened, the car notices.

When the boot is opened, the boot light does come on.


All the wiring in the boot appears to be fine. No signs of fraying or wear and tear.


Any fuses I should check?
Neil H

AND check the boot light isn't on all the time!
Bruce Caldwell

>> If the boot light works then the lock switch is working and therefore it must be the key switch closed all the time.

In which case, how do I open the key switch?
Neil H

No, with the latch set with a ball-point, the light goes off.

When key opened, it comes back on.
Neil H


The boot light goes on and off normally so switch and wiring is OK. The key switch may be faulty so check it's operation using a multimeter or fuse tester. Disconnect the switch first, at the connector behind the bracket which holds the lock. It may be that this switch is not operating and is closed all the time. I cannot simulate this situation on my car (to see if the lights don't work) because everytime I operate the keyswitch it unlocks the boot as well. Your switch may be stuck in the closed position.

I have to go to work in a minute so cannot help for much longer! Coming to the end of my six and a half hour lunch break.

Bruce Caldwell


Excellent.. - thanks for all the help.

I will take the switch out and have a good gorp at the w/e, then report back next week.

Much appreciated Bruce.., I'll add you to my 'must buy beers for' list on the next meet.

Neil H

if it helps, this is the behaviour I see on the Alarm ECU I have in the midget, I think it is down to the wires to the door sill buttons not giving a reasonable reading.
Will Munns

This thread was discussed between 10/12/2003 and 12/12/2003

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