Sometimes the instrument lights in my 2013 Grand Sport are off while driving during.

Once when this happened I rotated the instrument panel illumination control switch and the lights came back. But the last time I tried the same thing, the instrument lights stayed off.

If I push the switch, it toggles the map lights on/off reliably.

Should I just replace the switch, or could it be something else? Also, how hard is it to replace the switch?

 

Either dimmer switch has a problem that either cleaning or replacing it may fix the problem.

Or the ambiant light switch (or hvac controler that that sensor wires to), is having problems instead.

Simply, when driving lights come on, it dims the cluster lights, and when the driving light are off, the cluster lights get brighter instead.

So start with checking to see if driving lights are on in say daylight or garage, and if they are, then cluster should be dimmed.
If driving lights are on in daylight, then on the turn signal stalk, twist the dial clockwise (one that has auto on it) until you can turn it no more, to turn the lights back off, and speedo cluster lights should bright back up.
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If this solves the problem, hence dimmer switch if fine, then start with replacing the ambiant light sensor to later updated unit.

Also to point out, the new upgrade ambient light sensor dome is smoke tinted, while the older ones had a clear/frost dome instead.


Just make sure inside of car is warm, then take your time pulling up center grill so you don't snap off any of it tabs to replace the light sensor in it.
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And to note, if you start car up in darker area like garage where the driving lights will come on/cluster lights will go dim, then pull out into the sun light, will take about a min or two before the lights will turn off off on their own.

So start with turning the driving lights off via stock control/cluster should go brighter, and should be able to see if dimmer switch does have a problem to begin with by fiddling with it when the driving lights are off.

As for is new ambient sensor does not have everything back to normal in daylight driving (again, about a min before BCM will turn the driving lights back off in daylight from out of the dark), then may have to go the next step, and check the HVAV controller and connector for problems there.
Hence HVAC controller sends 5 volts to light sensor, and depending on the light the sensor sees, will send back a reduced voltage back to the HVAC controller. Threshold for BCM to turn the lights on, it about 2.9 volts or lower from sensor.HVAC controller, so either HVAC controller may not be either sending out full 5 volts to sensor in first place, or problem with it not receiving the correct voltage coming back (corrosion on connector pins or cold solder joint on header pins to controller board.
As for HVAC controller to BCM communication, that is a digital signal between the two,and if there was problem with that signal, would be getting a U code for that problem.

 

Thanks for the diagnostic procedure.

I experimented with it today in the garage with the garage door open. When the headlights are on, the instrument lights are off completely and the dimmer switch doesn't seem to have any effect when I rotate it.

When the headlights are off the instrument lights are lit, rotating the dimmer switch does nothing.