I have a 2014 IS350 Base RWD with only heated seats. I swapped the front seats (and switch) for heated/ventilated seats from a 2016 IS200T F-Sport RWD. All adjustments work fine, including the heated function, but not the ventilated function. None of the fans turn on and all lights do illuminate from the switch.

I have replaced the switch 3 times (tried with both model switches, FSport and Lux). I have replaced both fans on the passenger side. Cleaned all connectors (found a small amount of rust on the donor seat frames). Disconnected the battery for 15 minutes. Checked the four seat fuses (2x 30A and 2x 15A). I tested and confirmed 12v going to the bottom fans.

Any idea why the fans are not turning on?

The pulse generator comes from the switch I believe. I know that's working because the heating levels work fine. The seat adjustments and heating working tells me it can't be the fuses, relay, switch, or seats. So I've been looking at the wiring. As far as I can tell the wiring harness are the same for all RWD IS are the same and everything is pre-wired for upgrades. Including heated steering wheel (expect for the STRG HTR fuse and relay).