2013 Western Star Headlight Problem

The problem here is that my headlights stay on when the truck is running and parked, even if I’ve turned them off. To be clear, being that I’m in Canada, they’re actually the mandatory daytime running lights.

So basically, if it’s an extra hot night and I want to run my a/c by leaving the truck running, my headlights stay on. Throughout the winter, I found that this problem was intermittent depending on either outside temperature or dryness in the air (or both). If it was really cold and dry outside my headlights would shut off as soon as I parked and shut them off...if it was damp out and a little milder, they wouldn’t shut off.
Now that it’s summer, they’re just staying on...again, with the switch off and the truck parked and idling.