I know. Been there, done that. And when I check them all a second time, surprisingly, they are as they were the first time. Have done everything and more that Hayes suggests, but still no dips. Whatever the problem, it is obviously common to both lights. If I get an auto electrician involved (not out of the question) it will cost a small fortune to find a £3 replacement part. What else can I check? How do I test a relay for volts and continuity? I only know how to use a meter in the simplest way. Rex