w202 intermittent healight issue

[Mighty190]

1995 C36 with 160,000 miles. My headlights work about 70% of the time. When they fail the parking lights do still work but holding the high beam lever back does not work. So I'm guessing its a relay and not the switch.

Where is the relay located and is this a common issue?

Its been hard to test because they always seem to go out at the worst time when I can't deal with it and then work when I have time to look at it.