no lowbeam, no high-beam, passing lights work

[mrclubike]

That is why you have to do your voltage checks with the circuit under load
If you would have back stabbed the female connector hooked up to the switch and the head lights on
The voltage drop should have shown up

OK think I got you Mrclubike you mean by 'backstab' run a wire off the battery pos and hit the connectors to see what happens a each stage yeah that's a good tip (as long as you're carefull not to short it!).

No headlight relay on my bike, I should've just waited to check where the wires went, bit of a pointless question. Thanks for your info!

That is the  way to do it with a hot wire if you do not have a volt meter
But I was actually talking about using your volt meter
Put the Black lead of the volt meter to battery negative and back stab the connector on the key switch with the red lead of the volt meter. (With the lights turned on"loading the circuit")
If you would have seen battery voltage roughly 12 volts you know the connection and key switch  is good
But in your case you would have seen a lot less than battery voltage and then know that is were your problem is
Hope that helps in the future