Mondeo Intermittent Car Alarm

Symptoms:

• Car alarm keeps going off at irregular intervals (including at 3am, twice).
• Try everything to cure all kinds of possible causes (vents in the car causing draughts that trigger the sensor; windows partially open doing the same; broken door seals etc.).
• Sleep deprived madness
  

Cure:

• Replace the bonnet catch

The bonnet catch on a Mondeo is alarmed, and can only be opened with the car keys. If you try and open the bonnet, even with the keys, when the alarm is set, the alarm goes off. Since the bonnet switch is exposed to all kinds of crud, not surprisingly it can get corroded, switch itself on unexpectedly, and set the alarm off.

The new catch is very easy to fit (and I'm no mechanic). If you can't get a new catch immediately (but need to get some undisturbed sleep), just remove the alarm wire from the old catch - it's plugged into the bottom and can be pulled out quite easily. This stops the alarm going off, but also stops the alarm arming. You can get around this by shorting this wire: being a serial bodger, I just duck taped a hoop nail between the terminals.