I read on another site that some guys were having the same issues-they bought the "relay" harness-their problems were solved.I can't say either way.I do know that when I bought my FIRST set of Xentech's-the instructions stated to "run the lamps for about 5 minutes" on FIRST LIGHT UP.I did not see that in the DDM instructions.Could be what causes the lamps to intermittently not light up?I redid my connections on the stock connectors(Blue and Green ones)by inserting the leads of the bulbs straight in to the connector-instead of using the "plug" connector.Then once they were all lit,I siliconed the connectors so they wouldn't vibrate loose or anything.That solved the lighting problem for me anyway.It wasn't the ballasts-it was the connectors at the stock plugs in the stock harness.