In between the centre air vents on the R129 are two little buttons, one with a red square on it and one with a blue square on it. Press the red square button and the centre vents blow warm air; a little red LED illuminates in the button. Press the blue square button and the centre vents blow cool air; a little red LED illuminates in the button.

Now my question:

At night, with the headlights switched on, the red square in the button is illuminated (whether or not the warm air is switched on). Should the blue square in the other button also be illuminated? On my car it is not, only the red square lights up. The LEDs in both buttons work correctly, it is the blue square itself I am wondering about. Should the blue square be illuminated with the other dashboard illumination?

TIA

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JJ Rodger
2013 G350 Bluetec
1999 SL 500
1993 E300 diesel T
1990 190