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MG MGF Technical - Alarm - it's that time of the year

Every year, without fail, my alarm goes haywire !!!

I'm guessing it's due to the cold damp weather - but I have never got to the bottom of it. Is there a database of alarm related problems I could look at. I've checked the wiring loom in the boot, done the internal self test, WD40'd the door locks, etc... The only thing I haven't done is check the volumetric sensor thingy.

Basically - sometimes it's slow to deadlock the car, or when it does deadlock, the alarm keeps going off. I have currently disconnected the horn - but get some comments that the indicators keep flashing all night.

Any ideas what to check. ???

Not your battery starting to fail when it gets cold is it?

T Jenner

Almost all the alarm & locking problems I've had, on several Fs, have been the driver's door lock failing to make a good, clean connection. Corrosion of the connectors has contributed to this, which WD40 will only partly deal with - I'd recommend stripping the door lock out and giving it a thorough overhaul - nail file, sandpaper, electrical contact spray, etc etc. Get everything back to shiny metal & making a good connection and I'd be surprised if that didn't fix it. If not, the fault may lie in the micro switches inside the lock mechanism, although in my experience these fail permanantly, i.e. are not damp or weather sensitive. They are replaceable, but locating a complete door lock from salvage would be the simpler route. The wiring & connectors vary from early to late cars so best to check before purchasing, however the later locks can be fitted with some chopping & splicing of the wiring and since most of the problems are age-related, going for the youngest option makes sense.

Good luck, annoying isn't it ;o)

my alarm problem turned out to be simply a fuse; perhaps worth trying changing the relevant fuses as the cheapest possible solution.
CW Faux

How difficult is it to dismantle the door lock. Which connections should I clean.


It's fairly easy once it's out of the car. A digital camera is invaluable. I always think "I'll remember that, no problem", if only. If all the bits fall out in your hands when you take the covers off it's a bit of Chinese puzzle but doable. I think the problem is generally the micro-switches rather than contact cleaning. Then it gets more difficult. The basic switch is easy to find but one has a long actuator,I couldn't source one so I had to make one, very fiddly. I soldered the replacements in because I couldn't get a good contact any other way. If you don't like being beaten, go for it, if sixty quid or so is not a probelm buy a new one.


Got the locking mechanism out and took it appart and cleaned it. I think there is three micro switches - two clicked okay but one was a bit touch and go, (not sure what each ones does).

Anyway - put it back together and it superlocked okay - but again has stopped - so assume the problem to be there.

Are these units repairable. ?

Yup, definately the micro switch - had another look and one of the switches crumpled and the little black button pin fell out. I forced the switch in, (accidently), so now it superlocks - but when you depress the door pin to lock the door internally, it doesn't automatically lock the passenger side. I've had some bizzare quotes for replacement door lock mechanisms from 5.00 to 130. Presume the latter is new. All I really need is a new micro switch but can't find one ( Any ideas where i can get one.

(I assume the 5.00 is already broke as they couldn't confirm it worked)
D may be worth a try - they stock Cherry microswitches, or RS Components


This thread was discussed between 04/11/2008 and 24/11/2008

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