just to close out this thread.
I've now tested the fan and determined that the fan runs as per RAVE specs in every scenario except for when the temp exceeds 212 under hill climbing conditions. I'm a little at a loss for why it doesn't activate under this condition. broken sensor wire ?

 

What do you do when temps exceed 212, turn on AC? Do you let them get a few degrees higher to make sure the ECM schedule is not off by a few?

Believe broken sensor wire would also disable your temp readings. May have wiring issue between eng fuse box and ECM. May want to start by cleaning connectors and checking continuity.
......

 

Thanks Number9! so temps exceeding 212: If I do nothing, temps can continue to climb. Actions I'll take depending on how extreme the Pass i'm climbing include heater on full blast, pulling over (immediate temp drop once no longer under heavy load), slowing down and getting into the truck crawl lane (40mph up the mountain passes, me and the VW Westfalias) Normally my truck will run ~188, but climbing mountain passes can very quickly get the heat climbing. I'm trying to ween our Au Pair off of my Classic so that I can pull the D2 apart and install the oil cooler and inline tstat mod, but i cant help but think that I might need a larger transmission cooler to address the specific problem that I have.