We had a lease truck for work and it did the same thing.Dealer said there was a problem with the trucks and bad seal on the blower or heater houseing or something.
The truck was in the shop for that and the seatbelt light for two weeks.
They fixed the seatbelt light!!!!!
(Flag, AZ)

 

Interesting. You're the second person who has mentioned that. What year was the truck that was affected?

 

I had the same problem on a 05 3500 dealer has a tsb on the lights to replace. only if customer complains. Took it in and took about 3/4 hr. to do the work. two were cracked no charge to me. so far so good.

 

As an update, I have still had no success tracking this down. We had considerable rain again here yesterday, but the carpet stayed dry.

The mystery continues. I'm pretty sure it's not the cab lights.

 

my 03 qc seems to have a mystery leak, i don't think it's the lights. i think it might be the door seal,there is a seam at the bottom of my door which i think lets water into the cab. on another note-is this a tsb for 03s-exactly what is a tsb? i searched and didn't find much, i am well out of warranty(103k)

 

This is my current line of thought too. I cleaned the rubber seals at the bottom of the doors yesterday (they were CAKED with leaves, etc) because of all the rain we have had. I'm going to wait and see - before I let the dealer tear into it.