How I fixed my failed Nissan LEAF PTC heater

I have just been asked and reminded to share the information of how I fixed my failed PTC heater. So here we go. Please note that all the following information is NOT provided as a DIY repair guide, as I was not following safety standards and in most cases failed component are not same.

Just bit more about safety, as you can see from my previous post even "safely and professionally" designed heater failed in quite a spectacular way. That means components and design are not that safe at all...

Ok, enough rant, lets go to repair details. So after discovering why these heaters fail in the first place I had to make sure I fix the "cause", before trying to fix the "results". So, as you found out from my previous post, "cause" is a failed soldering on PTC element terminals. So I have cleaned all the terminals and PCB and used lead containing solder to solder these terminals back. Lead solder is much better for such applications as it sticks better and is more resistant to constant temperature changes, although much worse for environment. But I guess heater in rubbish bin is even worse for environment.
Yuck, not the nicest soldering job, I know... I have also repaired a missing trace on PCB just by soldering a wire to it. I have covered wire with few layers of insulating resin, just in case...

Then it was time to replace a visibly damaged IGBT (Insulated Gate Bipolar Transistor). Originally heater is equipped with AUIRG4PH50S, which is specially designed to be used in automotive industry. But I could not easily source such transistor so I just ordered a standard IRG4PH50S, because by looking in to "special automotive" version, I could not see anything special :D Unless exploding failure is something special... All data in datasheet looks exactly same.
I have also did a quick test on nearby components to make sure nothing else is damaged. And after applying some more insulating resin I decided it's probably time to put it back and see if I succeeded.

But before I done this I had to replace blown 30A fuse in DC/DC junction block. Which is a nightmare. Thank you Nissan!!! After few hours spent in freezing garage I eventually managed to replace that fuse and also did some "not manufacturer approved" modifications, to make sure, if I need to replace it again, it will be much easier. Sorry but I can't share this modification info with you here, for your own safety :D
So after fitting everything back together it was time to celebrate... NOPE...
Heater was not working and there was a fault code blaming PTC circuit 4. Time to take it out again.

Took it apart second time suspecting that IGBT driver is also dead. And yes, after checking resistance on 1ED020I12-FA driver pins next to previously blown transistor and comparing it with other drivers pin resistances, found out that it is also f%&*ed". Again without a success of finding needed part I went easy way and ordered similar "non certified for automotive industry" IGBT driver (1ED020I12-F2). This time datasheet was actually showing slight differences between them two, but I decided to use it, as I could not source the needed part anyway. Also 1ED020I12-F2 has 4 pins less, as 1ED020I12-FA has doubled corner pins.
Replaced IGBT driver, put everything back together and guess what... not working... Still fault code blaming PTC circuit 4. So this time I decided to take it off for a last time, if no success screw it... I got diesel heater installed already and can't be bothered anymore about this crappy PTC heater.

So took it off again and this time decided it's time to go over the components very carefully, testing every component on PTC circuit 4. After doing this, found out that IGBT gate resistor is also dead. Lesson learned... Always check everything carefully first time, so you don't need to struggle later.
I couldn't find the correct resistor in SMD format in my spare part box. So used what I found as I had no more patience with this thing.

Put everything together and... Not working... No more fault codes blaming PTC heater, this time fault code blaming high voltage wiring loom that goes to heater. So at this point I decided it's not worth wasting more time on it... But working on another project I accidentally discovered that leaving heaters settings on the lowest temperature and activating it remotely on the Nissan app, it kicks in. This must be a bug in Nissan software as it somehow misses a fault code. At least I knew heater itself is working. So I decided to give it a last chance, and found that by connecting and disconnecting the high voltage cables so many times somehow I managed to bend some small pins inside. After sorting this, heater came back to life. Although I am not using it anymore as I found diesel heater saves a lot of range in cold weather while burning very very little fuel. So I guess that's the backup option now.

As you can see such repair took a lot of time and nerves, so I would not recommend anyone else to try and sort completely failed PTC heater. On the other hand I would strongly recommend to try and sort it if it just begun randomly not to switch on, but still haven't blown a fuse in DC/DC junction block. That probably means your electronic components might be still fine, only failed soldering on PTC terminals needs sorting. But such repair must be done by a competent person, as it involves dangerous DC high voltage and a slightest mistake can be fatal!




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