Not sure if this has been mentioned before, but thought I would anyway. Upon attempting to sort my non working headlight washers on my 172 I discovered that the pump unit that powers the front and rear washers is identical to the pump that feeds the headlights. I called up the motor factors and they had no pumps for headlamps. So priced up a front and rear one which came to £7.72. Fitted this new pump in place of the old headlamp one and hey presto I now have functioning headlamp washers ready for the MOT. Cheap and easy fix for £7.72