UKPassats

Installed aftermarket HID kit years ago and they worked like a charm. Recently one of the ballast had gone faulty. I bought a new kit which is a different model ballast and replaced the faulty ballast. Bulb keeps flickering on/of at start up and sometimes switches off. I swapped the new ballast to the other side and it is the same. Last week my car would not start. Got halfords to test the battery with ignition off and their device read that the headlamp is drawing power. I am lost and I don't know what to do.