Check the fuse which is a in detachablepanel behind and under the steering wheel -three plastic turnbuckles. If blown, the cause is electrical or mechanical. If electrical, it could be a faulty switch (but is the rear wiper working in which case, not likely to be the switch), or a faulty motor. I had the same problem a few days ago and it proved to be a stiff linkage. To access, you could carefully remove the plastic black grille at the base of the windscreen and lubricate the joints - even WD 40 will do. You can also access the first joint by removing the wiper motor on the driver's (RHD) side. If you do, and if you remove the wiper arms it is essential to mark the position of the arm on its splines with a felt pen or Tippex so that they can be replaced in exactly the position they were. If you don't you will spend forever dismantling and adjusting afterwards.
jalewis@eircom.net, January 2009
