I do think the resistor has failed. I performed tests in other threads: unplugged thermal switch, then used paper clip to jump black to brown-white, the fan runs on high. Then paper clip to jump black to brown, relay clicks but fan doesnt run.
If I jump 2.5mm blue to 2.5mm brown (bypass resistor?) I think I will overlaod the 2.5 wires. Bypassing the resistor this way simply provides redundant high speed supplies. Shouldn't high speed have 6mm - 40A wire ?
I saw your thread where you swap brn and brown-white relay control. That does protect against overlaod. But you dont need to bypass resistor if you do that. Now the low temperature (198F) contact in thermal switch controls the high speed relay with the correct wire size (larger). The low speed relay and (bypassed) resistor are not utilized, unless the temp goes to 206F, but the fan is already running on high.
Thanks
Rick