Working through few repairs on my Audi A4 and one outstanding problem I have is the rear heated screen is not working.

The heated mirrors work when heated screen button pressed on centre console.

I have checked the 40A fuse and relay and they are okay. The screen isn't oxidised or any signs of delamination.

I have also checked battery voltage which is 12.3V when static.

Any ideas on what it may be before I start to strip trim out to chase things?

The points most susceptible to damage are the terminals where the supply connects to the heating element. Have a good look at them first. If possible, test for power at those terminals with a volt meter.

It would also be worth inspecting the wires that pass through a rubber bellows between body and boot lid. They have been known to break with the repeated flexing as the lid is opened.

Okay thanks.

I assume the connections will be behind the trim on right side of boot is that correct?

I had heard there may be some filter module that it goes through as well. There are a few electronic modules in the area around fuse box but not sure what they are. Any idea about them?

No, I don't know the location of the terminals. If you can see the element it should point to them.

Stripped some bits of to check wiring and got to terminal block for rear heated screen. 12V switching on and off via switch on climate control unit so I can only assume elements have gone on the screen. 12V on strip on screen.

Am I correct in assuming this?

 

If so does anyone have an idea how much replacement rear screen would cost?

Can you see a break in the element? If so it may be possible to repair it with conductive paint.

https://yourcar.co.uk/best-heated-rear-window-repair-kit/

 

Not really easy to see but looks like may be several breaks in heater element.

Thinking it may be new screen required 

Your choice of course, but a little pot of paint would cost far less than a new piece of glass. Do let us know the outcome of whatever decision you make.