Ranger
That's exactly what I did. Jumped 12V from GH (and GL separately) to the Y terminal and there was no response.
I have the situation where one test would indicate that the board has failed (the above test) and another test would indicate that the thermostat has failed (only .8V on the Y term supplied by the thermostat). Seems like an impossible situation unless both the board and the thermostat are defective.
I have ordered a thermostat to see if that fixes the problem. Like I previously said, they're only $20 or so and I need to get this thing fixed. If it turns out that that a new thermostat produces the correct result, I'm done, otherwise, I'll see if I can find a new board. They're pretty scarce right now.