Electrical problem
1998 Chevy Suburban V8 Four Wheel Drive Automatic 14000 miles
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Hooked a trailer up to the rig, and the left turn signal/brake stopped working. Front left flasher still works, but flashes very quickly. Trailer brake/turn still works, but flashes fast. Replaced all the bulbs, didn't fix it. Repalced the trailer hitch wiring harness, seeing that the problem started with the trailer. Didn't fix it. Changed the #16 fuse. No go. The back-up light and tail light still works fine, but the turn signal/brake light will not light up, and the hazard switch will not light it up either. Where should I look next?

Thank you