Model #EW30EW55GW3, this built in single ovens cavity lights would remain illuminated no matter what position the door was in and would not turn off using the control panel button. This problem would normally be an issue with one of the light switches, but with the electronics is this model, you need to look a little deeper to find the source of the problem.
Typically an ovens interior lights are going to turn on and off with the opening and closing of the door. This is done through the use of a push button switch, often mounted in the door frame, and the contact of the door with the switch will open and close the electrical circuit. Lights are wired in series with the switch (and parallel with each other) leaving us a very simple electrical circuit. Some ovens will also have another rocker or push button switch mounted near the control panel to turn the interior lights on while keeping the door closed. This is simply done by wiring the two switches in parallel with each other. That way if either switch is completing the circuit, the lights will illuminate.
This oven, being a bit more sophisticated (read complex) still uses a push button door switch mounted to the door frame, but when this switch is actuated, it is simply completing a low voltage circuit back to the control board. The switch at the control board is part of the display instead of an actual switch, so our control board will sense when the panel button has been touched and will turn the lights on. To complete the circuit to the lights, the control panel will communicate with a triac board that provides voltage to both the convection fan and both of the interior lights.
Because the triac and control boards are 'talking' to each other, we can only verify voltage is present to each board and then make some educated guesses as to which board has failed. I did a voltage check at the triac board connector on the VCC line to the ground line (use it, not the chassis for proper readings) and found 5vdc between the two. Next I checked between the communication line and ground and found 4.8vdc, which according to Electrolux means the two boards are talking. The final check was to start a convection cycle since the triac board also controls the convection motor, it the boards are indeed talking, the fan should still work. And sure enough it did, which leaves the triac board as the failure
After replacing the triac board with a new one (part #7316519200 BTW) the oven lights now turn off as they should. Because the Electrolux branded products come with a commitment to limited down time in the event of needed service, the most likely parts are sent to the customer prior to a tech arriving at the call which is a nice way to get the call done. At least while these things are still under warranty, looks like more first time completes for the techs. Not sure what happens after the warranty. Moral of the story. The oven works great.