mine 85 C10 did that and it was the electric door lock solinoid was old and was trying to freeze up. i replaced them with ones from a wrecking yard and it fixed except i got a bad plug on the passenger side, just to lazy to pull the door panel back off. hope this helps and good luck
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Jeff Dodson
85' C10-LWB 350/700R4
ANGLETON TX.
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2004 Silverado Crewcab (Dark Spiral Gray)
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