I had a hard time getting to sleep Tuesday night, as my brain wouldn't stop thinking about the MSTR WARN annunciator dimming. I finally came up with another possible idea, and was able to go to sleep. I tried my concept out last night, using a bunch of jumpers with alligator clips to hook up a test - I couldn't get it to work. I finally gave up in frustration.

I pondered the problem a bit more today, and eventually realized that I hadn't properly hooked up the jumpers to test my concept on Wednesday. I had another go at it tonight, and managed to get the MSTR WARN dimming working. The only catch is that it is a bit too dim in dim mode, so I need to purchase a different value Zener diode to sort that out.

I was able to get the dimming working by tapping into the trim indicator dim signal, which is run from the second poles on the BRT/DIM switch. Hopefully I'll be able to find a suitable Zener tomorrow, so I can get this working this weekend.