Heated windscreen

[steamship]

Originally Posted by hunker7

I think that's the next step, take off the module and have a good look at it. There are 4 wires, 2 from battery to control unit and then 2 that go to windscreen I take it?

Not quite. One is a control line from the HVAC unit, which I assume is the connector on the left of the picture. The brown and red cables (thinner than those from the battery) go to the windscreen itself and split in two somewhere as there are two connections at the top and bottom, which probably eliminates the possibility of a fuse under that cover.

I suppose to cover everything you could start the car, switch on the front demister (assuming it's cold) and then check if the boot module is putting out any power. If it is then that should eliminate the control line from the HVAC unit, the HVAC unit itself and the boot module, with the possibility being a break in the lines going to the screen - Just thinking, with VCDS, you might be able to check the measuring blocks to check what the temperature sensor is reading (since that is part of the criteria). A continuity check of the lines going to the screen would be next but would be awkward considering the extremes (from boot to windscreen), and then there is getting access to the lines at the windscreen end. The top ones you can get to by removing the overhead panel, but the bottom ones are somewhere near either corner, unless you can find them somewhere around the base of the A-pillar.