My Heater also failed with the same 2 fault codes. I tried to find a replacement one but they are like 800 EUR + installation costs.
So I searched a bit and found a guy that installed a couple of 12V, 200W PTC heaters and run them from the 12V system. The only problem with that is you have to control the stuff manually and if you manage to forget those on, they will deplete your battery blazing fast, or even worse, catch on fire (although unlikely). So I bought the OVMS module, added the missing metrics for set point temperature, heating and vent status and wrote a heating assist plugin. In turn, this allows the heater to be controlled automatically by reading the OEM Climate control metrics from CAN bus with the help from OVMS module. And last, but not the least I did not like those heaters dangling around above the dash so I took away the broken high voltage PTC heater and put in two 12V 200W PTC elements in it's place (better have, I was originally concerned about the load for the DC-DC converter being too high, but after around a year of using it it does not seem to be a problem). I tried to sum all this up in the video, so here it is.
All in all you can build yourself a 10 times cheaper heater for less than 40 EUR. And if you want the comfort of automatic control add 100 EUR for the OVMS (which adds a lot of cool features by itself).
If you have any questions please leave a comment below the video as I don't visit this forum so often.
EDIT: Updated Heating Element count as 2 elements were not powerful enough for defrost during -10 Celsius or bellow. Also you no longer have to compile OVSM as my code has been integrated in to the main releases.
Finally if you are interested in having the same setup, here are the main things you will need:
If you want to enable automatic heater control as well, you will have to:
NOTE: For heating status to work, the Climate control system must be turned ON before switching off the car.