97 dakota brake & abs lights only after heater core changed

had my heater core and evap. core changed.... now when i hit a bump just right these lights flash on and sometimes the dash backlights get dim, sometimes the hazard lights stay on for a second. most times it is just the brake light that show.... any IDEAS???

double check the main harness connection for the dash, possibly a bad connection and check for loose ground wires near the dash reinforcement and/or body.