Ford Mondeo 2.0 TDCi Battery light on constant

[wotan]

Alternators usually have their rectifiers / control circuit incorporated, there may be exceptions, providing you get one off the same make of vehicle then you should be ok.

Wotan

 

[ACIDTECHNO]

I had same problem, same engine but in a Focus. Luckily alternator was changed under warranty. After a quick search it appears it's a very common problem with these engines.
I'm having starting problems now, but thats in another topic (hint hint)

 

[Nitronick]

Alternator has failed. Dont matter if its the diode pack, regulator, stator, rotor, windings or what ever as the Alternator is a sealed unit so will need replacing as a whole. Gone are the days where you could whack a brush pack in and get the alternator back up and charging.

The reason the light goes out and comes back on and all high drain circuits are cut out is down to the Body Control Unit. The BCU is effectifly a computer controling everything by Can Bus multiplexed wiring. Once the BCU senses low voltage it turns off high loads to prolong battery life and illuminates the battery warning light.

Sadly Ford Rotating Electrics are prone to failure.