I think I have a problem with my 2002 Focus 1.6 speed sensor. I have
only had the car two weeks, and was told by the previous owner that he
had the speed sensor replaced about 2 months ago.

The ususal speed sensor problem of the speedo dropping to zero and the
car becoming jumpy like its not getting fuelled properly occur.

However this problem only occurs when i have the cars lights on and
then switch on the heated front and rear screens. Its like power to the
speed sensor suddenly goes when I am drawing a lot of current from the
battery, when I switch the heated screens off again the speedo
immediately starts working again.

Could the problem be that the battery is on its way out or could it be
a loose connection with the speed sensor or some other electrical fault
or even alternator?

Any ideas would be appreciated before i take it to a garage to be
looked at.

Thanks,
Dan