I drive a Chevrolet Cruze 2011 and about halfway home the dashboard lights dimmed. I don't have an adjustable knob.
Is it as simple as replacing a fuse or battery? What could be the cause?
Some of the newer cars automatically dim the instrument lighting when the ambient lighting changes. In other words, dim them at night so it is easier on the driver's eyes. Unsure if your car is equipped this way, but I did find where the adjustment knob should be.
According to the Owner's Manual;
The thumbwheel is located to the left of the steering column on the instrument panel.
It looks like this;
This feature controls the brightness of the instrument panel controls and infotainment display screen.
Considering you said they "dimmed" and not went off completely, it is not a fuse. This knob may have been bumped, causing it to dim the lights.
If the headlights are bright and the dome light is bright then you probably need to reseat a fuse. Open the fuse box and look for the labelling that points to the interior fuse. Pull it out and reseat it. It isn't blown, but may have a high resistance connection due to some corrosion building up.
The other thing that just crossed my mind is that you didn't mention if the headlights were on the entire time or not when you noticed this. If you turned on the headlights the dashboard may dim because it thinks it is getting dark. Is this car new to you?
2016 Chevy Sonic The last 3 weeks or so I would get in my car and my dash light would be all the way low.i would turn it back up and it kept doing this Couldn't figure out why. Yesterday left teen in car while I was in store she had music on. About 15 minute came out and it was Dead ,jumped it, took it and had the battery tested it was a bad battery. a least I am hoping I fixed the problem. the reason I am writing this to share the first sign in my car for a bad battery. have a great day, Georgette