2003 Ford Mondeo alarm going off

Don't know why it only goes off at night , but this might help you from previous posts on alarm probs .

A common fault with that car was the bonnet switch , but many other possible causes .


I think this refers to earlier Mondeos , but might help .


http://www.mirez.co.uk/AlarmProbs.htm


And this from another forum.

2003 Zetec S - alarm problem. - paul c
I think this may help.
Put the car into test mode by turning the ignition on whilst holding the heated rear screen button. When you release the screen button you should get a chirp. Now test each alarm input sensor ie door switch boot open close etc each should be greated by a chirp. This means the signal was received. I found that the bonnet switch was defective on my car this way. I suspect you may have the same problem.