The ETM shows a black wire providing power to the heater element, and a brown wire providing ground. Both are 2.5, so they will be substantial. So you can unplug the connector, remove the back off the car side connector, and:

- test the brown wire for ground
- depress the switch (engine may need to be running) and see if you get 12V between the black wire and brown wire

Then locate the pins on the top side connector where the black and brown wires connect. Test the continuity between these pins, and you should see some resistance since that's what generates the heat. If there is no continuity/resistance, then the element in the window is probably bad.

So if you have power, ground, and continuity, you should have a working defrost.

__________________
Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe