Hey guys wondering if there is any fix to why only 2 lines on the rear windscreen demister work, is it fixable or would I need to get a new windscreen

new screen is the best option if available and right price

other wise repco - supercheap or similar and purchase rear demister repair kit
should have instructions with it but is basically a metallic areldite which is applied to the breaks in demister element -(a bit fiddly)

remove covers - demister on - "carefully" connect one end of voltmeter ,(20volt scale)to one connection of demister - touch other end of voltmeter to a piece of alfoil and starting from end where you have meter connected to demister -slide alfoil across demister lines until meter changes reading to find area of break in element
slide back and forward when you get a reading to narrow down location of break.....

circuit is working otherwise you would have no lines
breaks can be hard to see and may have more than one break sometimes
if it is taking awhile allow demister to cool down occasionally.................

hi, i've used a repair kit for rear demister with great success. you need to look closely at each demister line for breaks and use the metallic paint to join them up. it's fiddly but if done right it works great,
cheers, shaddoweaver