Common problem on the Mark 2 Mondeo. I had exactly the same with mine and just couldn't fathom out what the problem was.

As elekie says, I can't remember whether you need to just unplug the connector or join the wires together to do away with the bonnet sensor, either. But if you just unplug the bonnet sensor and then try setting the alarm you'll soon find out! If it goes off immediately then you will know that you need to join the wires together.

Alternatively, you could do what I did when I had the same problem and buy a new sensor. About £35 from what I remember, though you could probably find one on a car in a breakers for peanuts. However, as you've found, they do give problems.

After I'd changed mine I dismantled the old one and discovered that I could have, in fact, cleaned up the internal contacts of the switch and it would have probably been OK again.

So, that's three different options. As they say on the TV, "The choice is yours!"

Edited by Galaxy on 20/12/2015 at 14:49

Just reporting back.

After disconnecting the switch the car runs normally but does not flash the indicators on the second locking.

After shorting the supply wires to the switch the car runs normally and the indicator flashing is restored on the second locking.

In neither case does locking the car with the window partially open and then inserting an arm and waving it about set off the alarm.

A new switch from Ford comes out at about £45 so I might go ahead with that. The parts man had the number in his head, he had supplied so many of these in the past.

Hello Galaxy,

Thanks for your detailed reply. The car is an Si V6 and I always assumed that it had motion sensors fitted, since it mentions them in the handbook, although I have been puzzled because they weren't obviously visible. On relection, I think you are almost certainly correct. My excuse is - I've only had the car nearly 17 years!

I did look at on-line dealers but by the time postage is added it came out to be about the same price. Our local dealer is within walking distance. I haven't had any luck finding anything on ebay.