Low tail light voltage and no lights

[Dachdu69C10]

Hey guys I'm having issues with my tail lights, I made a new harness from the firewall to the lights themselves, I have 10v with the brakes applied at the firewall connector, and it goes from 10v to 3v with the blinkers on. All the wiring is done the way it would have been factory. And each brake light has a ground from the housing to the underside of the bed. I also have 10v at the bulb sockets and new bulbs but no light at all. Any suggestions?
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