2012, P311c and P3176 after replacing PTC fuse.

[Kedelstam]

Hi,

I recently bought a 2012 leaf with no heat but driving.
Previous owner replaced heater at workshop but not the fuse in DCDC junction box.

So I followed the tutorials on YouTube for replacing the PTC fuse and found the fuse as expected to be blown.
After putting all back together I got P3176 and P311c and car won't go into Ready mod e.

I see many threads saying cause for these codes are pre charge resistor in HV battery JB. But for me this don't feel likely after the work I have done.
I'm leaning towards human error from my side by failing to connect something in or around DCDC junction box or can i somehow have made damage to the inverter capacitor?

I'm starting to lack ideas on how to proceed with this, and would like to narrow down the possible causes before removing/ replacing DCDC junction box or pre charge resistor.

Any ideas?

 

[RNeil]

The inverter has a very large capacitor. If this is not charged before the contactor closes, you would have excessive contactor wear and maybe it would weld shut. The precharge resistor provides low current to charge the capacitor before the contactor closes. The controller requires that the capacitor has close to battery voltage before closing.

The precharge resistor is in the area you were working on. It might be damages or not connected right. More information: https://www.diyelectriccar.com/threads/2011-leaf-died-when-left-the-defrost-on-for-20-minutes.197746/

 

[Kedelstam]

Sorry for my late reply, but I wanted to have some facts before making another post.

I was able to confirm a broken precharge resistor by measuring 12v dc on pin 11 in connector B24, the one going into the HV battery. And no 400v dc going in to the inverter, by opening the small cover on right hand side of inverter (I don't recommend doing this I your not a trained electrician with propper tools and knowledge!!)

After removing the HV battery and changing the resistor for a new 30ohm resistor I took a measurement on the HV cable going to DCDC junction box.
This measured only 180ohm, far below the expected >3kohm. After unplugging the PTC heater value was 40kohm.

Car now starts and drives with no heat, just like when i bought it. And the PTC heater failing with 180ohm explaines my symptoms.
Feeding 400V over 180ohms gives only 2,22A well below the PTC heater fuse 30A. But it gives an effect of 888W burning the precharge resistor with in a few seconds.

So conclusion being that the previous owner replaced the heater with an broken used heater. And while I was replacing the PTC fuse I did measure the PTC heater and found it giving a ok value using my personal cheap multimeter, the faulty value I found using a more expensive multimeter. So when working on this I recommend using a professional multimeter, if I had I would have saved myself the trouble of replacing the precharge resistor.