My truck has 198,000 and runs great but yesterday the right turn signal light on the dash was lit when I started the truck and never went out. When I turned the left signal on it worked fine but the right signal would not flash. I looked at the lights and the top bulb stays lit, wont flash when I signal a right turn? Later in the day I started it and it went away, everything normal. Today back to staying lit?? What does this mean?? Thanks..