This procedure assumes that the system operates normally with the black box not installed. If the system operates abnormally with the black box not installed, click here.
If both headlights cycle repeatedly after driving through rain, you probably got water in one of your black boxes. In that case, you will need to take them out, dry them and reseal them thoroughly. Otherwise try the tests below. The tests requires a continuity tester or Ohm meter. These are readily available at Radio Shack, or inexpensive multi meters are also available there, and also at most auto parts or discount stores. Follow the manufacturer's instructions for continuity checking.
With the circuit de-energized, disconnect the new connectors and remove the black boxes.
Check for continuity (no resistance) through the black box by checking each wire on the 5M1F connector with the corresponding wire on the 1M5F connector. All wires should indicate continuity through the black box (from connector to connector) except for the white wire.
Check for short circuits in the black box by checking for continuity between each color of each connector on the black box (i.e. brown to red, brown to yellow, brown to green, etc.) Ignore the white wire. All individual wires (except white) on each connector should NOT have continuity.
If either of these checks are not correct, open and inspect the black box. Check for broken solder joints, crossed wires, or an incorrectly wired relay. The relay should be wired as follows:
A jumper should also be installed between terminals A and 3.