[QUOTE=e34.535i.sport]Hmmmm that is interesting... I can see how the fuel filter can rob power (mine weighed a ton when I changed it - although it was about 14 years old! LOL!), but why would problems only arise when the A/C is on if this was the case?[QUOTE]

Gradual power loss is hard to detect, at least until some major milestone like accelerating past 50-60mph isn't met. I bet your friend doesn't do many top-end runs, otherwise she would have noticed the new, lower top-end speed caused by the reduced power.

Or, did the fuel filter/pick-up screen in the tank finally plug up totally causing the very low power output? Hopefully, this junk didn't make it into the injection pump and injectors yet as now you are talking tons of money.

Most cars provide pretty easy access to the in-tank fuel pump which means you can put eyes on the condition of your friend's bio-project (or not) in the fuel tank. It should be not much more than a couple lids and screws but I am not the one to know about European model Ford diesels!

Brian