Okay now I'm posting a follow-up since I did replace my 2012 LEAF SL PTC heater myself. Prior to replacing it, I confirmed I still had power (~390 volts DC) coming from the DC>>DC converter with a voltmeter at the heater plug. The 2012 version heater has coolant flowing through it too. Once I figured out what the PTC heater looks like and found it under the hood it took me 8-10 hours to replace it with a salvage yard unit, (paid the bargain price of $225, although $500 is more typical vs. $900 new). There are 33 fasteners involved in removing the PTC heater, (about 8 of them are clips, mostly bolts, and two hose clamps). Not easy but you can figure it out once you realize you have better access by removing the drivers' front wheel, & wheel tub & 12 volt battery & its tray. The trickiest part was actually the unplugging of the orange power cord from the heater. It must be done in a 3 step sequence by pushing tabs at the right moment while pulling. So in my case the Nissan dealership mechanic didn't do a thorough diagnosis & investigation... He gave up after reading fault codes. There was no issue with the DC>>DC converter after all. I cleared my codes via my LEAFspy pro, and they have not returned after 2 weeks of winter driving with heat. I'm very happy I could fix this myself for $225, as the dealership had quoted $4,000.
