Central locking alarm - major, wierd problems with central locking alarm - Mark 2.5

Technical Area Electrics & ICE
2

I have a 52 plate mx5 sport. Over the last month or so an intermittent problem seems to have developed with the alarm…

I will use the remote to double-lock the car as usual, then walk away. Randomly, usually after a few minutes, although the last time it was seconds, the alarm comes on and the remote doesn’t turn it off. In order to turn it off I have to put the key in the door and open the car.

This is where it gets more wierd…so the alarm is off and the hazard lights/indicators have stopped flashing but there are numerous lights on the dash lit up almost as though the key is in the ignition and half turned!. E.g. engine management, ABS, Handbrake, battery, and alarm lights. Also the reversing light was on as the car was parked in reverse.

This is where wierd becomes insane…in order to try to reset everything, turn the insrument panel and reverse lights off I put the key in the ignition and started the engine. It started perfectly so I ran it for a minute, turned the engine off and removed the key. HOWEVER, the engine was still running despite the key being taken out of the ignition! I could rev it as normal. There was literally no way I could turn it off so I had to stall the engine!

This did turn all the lights off (as well as freaking me out!) and I thought might have reset things. I alarmed the car again and all seemed fine for 8 hours until 4am in the morning when I was woken up by the car alarm! Exactly the same as above happened i.e. had to enter by using the key as the remote locking would not work at all. All the lights were on again so I started the engine and yet again it wouldn’t turn off even with the key out of the ignition! With the fear of becoming very unpopular with my neighbours I disconnected the battery and have locked the car manually.

 I hope someone can help with this one cause it has totally fathomed me!

Regards,

Phil Roper

3

It would appear that the alarm is sounding because the ignition is switching on, which subseqently de-activates the alarm fob.

I cannot give much more insight than that, but I would be tempted to think of a knackered ignition barrell, but somebody else will be able to give more detail in to that - but I’m fairly sure that is why the alarm is sounding, and why it won’t stop.

4

Whoa! You’ve got some issues there! With that many electrical gremlins I’d suspect water ingress into a major component… or a faulty ignition switch as suggested. You may need to get it to a garage if you don’t have much electrical knowledge.

5

 Thanks guys,

I think I’ve discovered the problem. There are 2 wiring plugs (not sure of the correct term) just behind the “off-side” front headlight. Basically LOTS of water must have been spraying up over a long period of time as I literally touched the wiring there and one of the wires dropped off due to corrosion! A pretty major design problem on Mazdas part I think. I heard something click and instantly the problem was solved (ish)!!! The alarm works as normal and the engine stops if you take the key out! I have no idea what the wire does but will get it re-connected pronto.

I think the failing/poor connection of the wire must have been shorting or bridging a circuit somehow???

Thanks for your help and advice,

Phil