Front Brake Switch mysteries, 1991 K100RS

[BoardOfCan]

My front brake switch does not light up my brake light. Rear brake switch works great. For its age, bike is LOW mileage and was carefully kept by the PO, wires look nearly new all around.
I HAVE NOT tried replacing the actual switch proper, but unplugging and putting a continuity tester to the wires coming from the switch tells me the circuit is opening and closing per normal.
Wires from the plug to to their intended spots at the light fault finder and big signal relay. I DID replace that relay with a spare, same result.
I hate to go through the misery of replacing the switch at the lever before putting the question to yall - am I missing a possible point of failure between switch, plug, and relay/fault checker?

[frankenduck]

With the bike on and the kill switch straight up (it kills the brake lights too) pulling the lever you should get 12V at pin E1 where the Gray/Red wire  (front brake switch) enters the BMU. (Bulb Monitor Unit)

[BoardOfCan]

Thank you, I'll check that. If it fails, switch?

[frankenduck]

Yes. If that doesn't work and Fuse 1 is good then it is probably the switch.

BMW: 61311459870  $50

If you re-use the wiring from your old switch, 5 of them for $4 at Amazon:

https://www.amazon.com/Switch-SS-5GL-SS-5GL2-SS-5GL13-SS-5GL-F/dp/B0B3NBXQMG

[The Mighty Gryphon]

Clean all the connectors in the brake switch wiring with Deoxit and if the problem persists get the switches the mighty Duck has recommended. 

That front brake switch had to be replaced twice in 8 years due to brake fluid and other junk getting into it on my 16 valve RS.  The micro switch used isn't really sealed against crap getting into it.