1st part of big 3 failure?

i upgraded the negative batt. to ground yeaterday and my headlights look extremely dim now. i thought it was because i did not sand down the new ground location to bare medal. i did that today and they still seem dim. i checked my batt.  wit a multimeter and off its about 12.9 volts, headlights on 12.2, high beams 12.05, car on highbeams and music playing 13.92 volts. could i have maybe done something wronge with the upgrade?

Did you leave the factory ground wire as well?

yes, and i used 4 awg wire and soldered the terminals after i crimped em

List your vehicle information. Many vehicles use two ground wires from the battery to the vehicle. Some go to the body and some to the engine. Use a volt meter set to DC voltage and measure from the negative battery post to where you terminated the ground wire. Start the vehicle and check your measurement. If it is higher than 0.2 volts you have a bad connection or wire.sparky