2004 focus 1.8 tdci fan belt

last night fan belt came of just driving at normal speed .power steering went and battery light came on belt is not snapped.what could cause it to come off.not got ramps or anything to get under it to see if tensioner has failed or could it be something else.think its the original belt as i have had it 7 years and not changed it.66k on clock

It sounds as if it may have stretched. Try adjusting it or change the belt completely for added peace of mind. 7 years is good going for a belt.

hope it is just the belt much cheaper than the tensioner.think its a garage job tomorrow.thanks for reply

got the car back from garage it was the tensioner that was gubbed all sorted now