The sun load sensor determines how strongly the A/C should run. I wouldn't be surprised, though, if it also affected heater output. Nonetheless, I wouldn't expect zero heat from a faulty sun load sensor. I do hope that I'm mistaken, for your sake. IIRC, the sensor is located in the top of the dashboard, or up by the mirror.
Brilliant Silver 2021 Leaf SV40 W/ Pro Pilot & Protection
2009 Vectrix VX-1 W/18 Leaf modules, & 2 lithium E-bicycles.
BAFX OBDII Dongle
PLEASE don't PM me with Leaf questions. Just post in the topic that seems most appropriate.