This specifically relates to the Generation 1 Nissan Leaf PTC Heater Repair. No heat in the cabin is the symptom.
I randomly saw this car on eBay recently: 62 Plate, 38k miles, 1 owner, Full Nissan History but no hot cabin air. The inside looked MINT!
I literally couldn’t contain myself. My heart skipped numerous beats. No point in trying to do a deal with the selling dealer – it was priced competitively and – let’s face it – he could see straight through me and my obvious excitement! I paid after a few messages – without seeing the car. I had an inkling the lack of hot air was a common fault but nothing else at this stage. Car was in Leicester; I’m in London. Battery health: 10 Bars. I’m driving that, right?!? No way I’m getting that beauty recovered on the back of a flat bed. Did the journey ok-ish. One charge at Junction 15A, Northampton. There’s a whole 2nd story in the faff that went into finding a working charger. I’ll save that for another time.
Ok, I’ll cut to the chase:
No heat. Confirmed. Fault codes for heater voltage and heater circuits present.
Specifically:
B2772 Positive Temperature Coefficient (PTC) heater voltage
B2773 Positive Temperature Coefficient (PTC) heater circuit 1
B2774 Positive Temperature Coefficient (PTC) heater circuit 2
B2775 Positive Temperature Coefficient (PTC) heater circuit 3
B2776 Positive Temperature Coefficient (PTC) heater circuit 4
Ok. We have a symptom. We have a fault and we have some fault codes. What’s the next step? Where do we go for some direction?
Obviously, the correct answer is a bit of system research: How does it work? How is it controlled? What else is involved?
Without getting bogged down, the PTC heater is essentially made up of 2 sides: the control side circuitry and the heating elements themselves. The control side takes its communication and prompts from the AC Control Module and in turn controls the heat output of the elements. The heat elements are powered via the HV system.
The control side is very simple to test: it is fed by a power, a ground and communicates with the AC Control Module via LIN. Very simple testing indeed. I do test communication networks with an oscilloscope – a meter is a little hit and miss in my opinion and doesn’t give the whole story. So. Control side verified and all good. I then tested the HV feed into the unit. All good. (This naturally implied the infamous 30 amp fuse was fine, too.) DO NOT DO THIS UNLESS YOU ARE EV TRAINED. JUST DO. NOT. DO. THIS TEST.
PTC Heater wiring diagram from a generation 1 Nissan Leaf
We have a faulty PTC Heater Unit. That is the only thing it can be as we’ve carried out methodical, logical testing.
Cost: £1950.00 + VAT from Nissan. Long term back order, no ETA. Lovely! (Actually, quietly super excited as I was dying to rip into the unit and see what was what!!)
Ripped it apart. Cause of failure: absolutely as per the gentleman who posted 2 articles online about the repair he did: Sub-standard soldering of the element connections to the board. Ok, I can repair those easily enough I thought.
What were my ‘knock on’ failures though? How had the control board itself failed? This was going to be my heart in mouth moment. My make or break….
Disclaimer: My knowledge and experience with PCB’s / Circuit Boards is Zero. Nada. Nothing. A few visible scorch marks. Something had happened here I thought to myself! Cleaned up the board, ordered a couple of books, spent time in front of YouTube, chatted with a local electronics store and visited my local Hack Space. (Read into that the best part of 2 weeks, dear reader…!) So – I’m sorry to say – my conclusion is exactly the same as the gentleman previously mentioned who has 2 articles on this subject, posted online: This board is 100% not worth repairing! My list of parts reads: at least 3 resistors, a capacitor, a link switch, 2 inductors and a diode. There will definitely be more that I have missed, too. I am absolutely not going to attempt repairs – or take things any further with this board! Disappointed? Yes. Have I learnt from it? Yes. Do I have a solution? Possibly. When I’ve found one, I shall edit this post and make it available.
Nissan Leaf PTC Heater Circuit Board showing failed compnents.
There are numerous articles / resources and YouTube vids that I returned to on more than one occasion. The least I can do is gather them here and credit them:
First article, mentioned above: https://ev-olution.yolasite.com/Nissan-Leaf-Heater-Fault.php
Second article, mentioned above: https://ev-olution.yolasite.com/nissan-leaf-ptc-heater-repair.php
Reasonably interesting video of the inside workings: https://youtu.be/cl49AHhV6FI
There is more that I will collate and gather here at a later date.
