How do I fix the lights for my heater/ac control in my car?

The car is a 2000 Dodge Stratus.

What are the chances that the dimmer (usually controlled by a dial next to the headlight control) was accidentally turned to low (or off)?

If the heater works – that is, blowing heat – I wonder if the dimmer was played with.

If your other dash lights work, t is most likely the bulbs,sometimes it quite extensive to take the dash apart to get at them,ask the dealer what they would charge to do it.
You might luck out and be able to access it from under neath and not have to take the dash apart to do it.

@elbanditoroso I checked the dimmer, it was all the way up. The radio and gauge lights are bright and the rear defrost light and the AC light on the two climate dials both work. The rest of the lights for the hot/cold, fan speed and the vent options do not. I guess I could live with it, but it is kind of bugging me. The heat and AC themselves both work just fine on each setting.

Ripping apart the center console is rarely fun, but it seems that that is what is needed here.

I guess you will have to replace the bulbs.

Replace the instrument bulb for that part of the panel. Just pull out the switch panel and pop out the bulb. Or check with you friendly neighborhood mechanic.