I had a 2017 MacBook Pro 15" with the left fan running at full speed immediately on power-on after a repair shop bungled a battery replacement.
I checked for the broken FET and sure enough:
[image|3393484]
Using the schematic and data sheet for the DMN32D2LFB4:
[image|3393485]
I found the two drain pads:
[image|3393486]
Then using enamel wire I joined them:
[image|3393487]
Which resolved the issue by tying the speed of both fans to the speed of the right fan. I'm unsure what consequences this will have on thermal/compute performance, but my assumption is that the heat pipe can transfer a lot and the left/right fans are not tied solely to the CPU/GPU temp, but some combination.