Rear heated windscreen wont heat up

There is something wrong with the heater.
14.3V across the screen shows you have an earth on one side and power on the other...but no load, well not much of a load. With the high power load of the heater, I would expect the rest of the circuit (relays and wiring) to drop some of the voltage. That shows virtually no current is flowing through the circuit.
At 80 Ohms that's only 180 milliamps drawn by the heater. The equivalent of 1/2 a Watt, not even close to enough.

At C3driver52's 1.6 Ohms, that's (theoretically) 9.25A. Resultant power dissipation of about 85 Watts. That's what you want to see.
It appears your heater repair hasn't worked. Well at least not all of them, because you have resistance there and not an open circuit.
Use your meter, on ohms, to check resistance from the contact on one side, to each of the tracks on the screen. Then check from the other contact to each of the tracks. Try various points on the tracks to the contacts. There is a break in the track between the high and low resistance points on the same track. So the resistance should go from virtually 0 Ohms to 80 Ohms on each side of the break in the track.

Cheers for the replies,
C3driver52 yeah they are both pushed in fully just long in the tooth a bit like me

took the rear cluster off and used that earth got a reading of 14.32 from the left connector and no reading from the right (Earth) connector.

Ozvtr checked the resistance all on the left are reading between 0.5 - 0.9 getting higher as i move it across the screen until yes i found some breaks that are still there so back to the granville electro connector it is, the earth wire looks fine from the right of the screen along to the rubber flexy boot and under the plastic running up the side of the boot into the roof. that point i stopped for now as im now set on it being more breaks that i need to find, annoying since they are small scratches and hardly noticable tbh

Yep found more hairline breaks, thankful for the multimeter as finding them would have took forever.

left side of the window is now showing 1.0-1.5 on resistance
right side (earth) is showing around 6.0-6.5 on resistance

seems better, will try it with power on volts tomm as it has to set for 5 hours before using it.

left side of the window is now showing 1.0-1.5 on resistance
right side (earth) is showing around 6.0-6.5 on resistance

right side is showing 14.0 - 14.2 on volts on the left on each line

it is working now but it seems all the power is being pulled to 1 certain line

Do you have window tinting on the back screen?
If not, what are all the white marks on the heater lines?
The heating seems to be concentrating around some of those white marks. That leads me to believe there is more resistance in those spots. Some form of corrosion?

You are dealing with what's known as a series-parallel circuit. You have to be careful as to where you take readings as the "parallel" circuit will interfere with your readings.
Forget about voltage readings.
You should break the rear screen into (virtual) segments from left to right (or right to left, doesn't matter). Measure along the lines from one side to the other but stick to the one method (left to right or right to left). Put one probe on one fixed electrical contact. The resistance should increase (proportionally) as you move the other probe across the screen and away from the fixed probe. If the resistance "jumps" up there is a problem between that point and the last measured point.
I am concerned with these spots that look like corrosion.

No its a normal window the white marks are the silver repair paint, even using frog tape the paint doesnt stay on the lines with the size of the brush they supply.

ill have another go at measuring and see where the problems are then

cheers

A couple of pointers that might help when repairing heated rear window elements.

The actual tracks on the glass are usually copper which is a very conductive metal. This might be either covered in a lacquer or over time, if it's bare copper it can oxidise. Either way it means there is a non-conductive surface over the copper.

Before you apply silver paint you need to expose/clean a small area of copper either side of each break. This can be done by very carefully using a mild abrasive, eg fine wet and dry paper. Go very gently and be careful not to rub the glass surrounding the copper track. I use 'Gaffa' tape to mask the glass either side of the track, it's thicker/tougher than masking tape and helps with the next part.

Silver paint is conductive but it's not as good a conductor as pure copper. When applied, especially over longer sections, ie anything more than a hairline crack, you need a decent thickness of paint. This is where the 'Gaffa' tape helps, it forms a channel to flow the paint into so you can build up a thicker layer.

And finally, when the paint is dry I run a fine scalpel blade down the edge of the tape before very gently removing it so as not to disturb the repair.

Good luck! With a little care heated rear screens can be repaired