If it blinks after a few seconds fast it probably is a bulb burned out. If there is intermittent problems with turn signals, windshield wipers, brights, windshield washer it is the MFS. Multi-function switch. TSB on that for the 2006 trucks I think. My wipers were completely screwed up of course in a driving rain storm in heavy traffic. Just replaced the MFS using this tutorial:
How To: Multifunction Switch Remove/Clean/Install - Dodge Diesel - Diesel Truck Resource Forums
How To: Multifunction Switch Remove/Clean/Install - Dodge Diesel - Diesel Truck Resource Forums