the headlamp switch corrected the front driver side parking lamp. After I cleaned the contacts in the socket connector the voltmeter showed full voltage. Still had all four corner side markers out. Checked the bulbs and they were all four out. I didn't think I would see or at least notice all four bulbs out at the same time, I thought for sure an electrical problem. I had full voltage to all four corner side markers. A while back I had blown the fuse and that may have been when all the bulbs popped.