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Hello and welcome to JA!!!
I'm Billy and i will assist you with this.
Indeed, the most probable reason for this problem would be the dimmer switch (as the latter controls the dash lighting).
However, before getting a new switch (or trying another switch), there is a bulletin on this matter. This suggests water ingress at wiring harness plug on bulkhead causing this issue.
So first you need to check the relevant wiring, make sure plugs, connectors and wires are dry and in proper order.
I will include the bulletin so you check all the details accordingly.
Click here for details
That should solve the problem. If not, the next step would be the dimmer switch.