what is the make of vehicle? some manufacturers rely on an earth passage via tailgate hinges which after a while becomes very poor,and may need a connection direct from screen to main body earth point to correct fault!
k
December 2012
if light comes on then the relay is working ,but it better you check the relay for continuity,i doubt its the windscreen heater matrix,unless its one of those stick on 1960 crap
mm
December 2012
Automatic Answer
We may have found other answers which could help you.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix cars.