Trying to fix my 2012 Leaf Charger

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Beard

New member
Joined
Jun 19, 2024
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1
Location
Virginia
Looking for advice if I should try the diode fix or just replace the OBC for my 2012 Leaf.

A couple of days ago, I noticed my breaker for my dryer tripped (I have an auto splitter for 220V charging). I didn’t anything of it, until I noticed the next morning that my Leaf didn’t charge. At 80% charge its range is down to ~35 miles, so it is kind of critical it charges every night. Plugged in the 220V charger, got one beep that it was connected, but didn’t get the double beep that it was charging. Tried my 110V charger: same thing so the charger isn’t the issue.

After reading lots of posts and watching EV Enhanced’s Video (), measured 4.5 Volts across the proximity port, but got infinite resistance both directions across the pilot port (i.e., no reading). I ran a code scanner for the onboard computer and nothing. I drove down the street to a local CHAdeMO charging station, and it charged fine.

I figured unplugging the 12V Battery for a few hours to reset the whole system couldn’t hurt. However, now when I plug in the 110V or 220V chargers, I get the one connection beep, the double beep for charging, but then a click 2-3 seconds later, and charging stops. Also, I am getting no voltage across the proximity port and still getting no resistance reading either direction of the pilot port. Still no computer fault codes.

Despite its minimal range, I love my Leaf (my wife and I can switch cars when we need to drive further). Curious thoughts on if the diode fix would be worth a try given this situation, or if I just need to suck it up and replace the OBC, or any other ideas. I am just not getting the same readings across the pilot and proximity ports or I would just go with all the other advice in these forums.

Thanks!
 
trying a diode is very easy. All the videos that I have seen show its a lot of work. NOPE... Take the plastic top cover off of the access to the back of the charging port. Remove the 4 bolts for the charger port. Unplug this orange cable under the cover. Now you can pull the charging port out a good 10 inches or so. Peel back the rubber behind the charging port this gives u access to the wires going into the port. then cut the white wire and insert diode. While its all apart you can see if this fixes ur problem. good luck. I'm going thru the same issue and its a cap on my power board
 
then cut the white wire and insert diode.
With all due respect i just don't see that this could solve anything if the D547 diode on the control board is blown.

If the diode is open on the board, then there is no path for the signal.

If the diode is shorted then the signal would be passed, but there would be no blocking-function for reverse current flow, if that were a thing of concern. The only concern would be that reverse current would cause the EVSE to shut down. But there is no current source on that circuit that would drive that line unless some accident inside the OBC would cause contact with another circuit path.

The only solution for a blown D547 diode would be to replace the diode on the board--there is no magic repair possible in the connector.
 
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correct if its open ... possible if its shorted ??? Am I not thinking correctly?
I read a lot of posts for people to try inserting the diode in series with this wire?
I see your point on replacing the diode on the board. I'll defer to your opinion :)
 
If the diode is open on the board, then there is no path for the signal.
True. But a lot of the time, a blown diode will fail shorted.

If the diode is shorted then the signal would be passed, but there would be no blocking-function for reverse current flow, if that were a thing of concern.
For J1772 standard compliant EVSE, it is a thing of concern. The EVSE should detect that the diode is not present, and issue a diode fail error. The reason is that if the plug has fallen into a puddle, then it could conceivably come up with the right resistance that says "ready for charging, turn on the juice", and someone could be shocked picking up the plug. Far fetched I know; let's call the J1772 designers visionaries.

Even if the puddle or toddler poking metal into the plug resulted in the right resistance to signal "ready for charging", it's not conceivable that it would pass the diode test. So that's the reasons for the diode in the on-board charger. If it did in fact fail shorted, then since the shorted diode is literally the very first thing that the control pilot wire connects to, then provided that the shorted diode is properly (low resistance) shorted, then adding the diode behind the charge port is a valid fix, and saves a boatload of trouble extracting the on-board charger from the Leaf.

I know some people that deal with EV chargers a lot, and they say that unfortunately a shorted J1772 diode is quite unlikely. Perhaps they would say that, since they charge money for repaired chargers. But even if the chances of success are low, it's such a relatively low effort thing to try, that it remains quite popular.

I note that some of the cheaper EVSEs don't bother doing the diode check, even though it costs just a resistor or two and a few lines of code in the firmware to implement it. If you knew of where to get such an EVSE, considering the low likelihood that the diode check will actually save anyone from electric shock, switching to a cheap EVSE without the diode check is possibly an even easier solution. No help at public AC charging sites, though.

But there is no current source on that circuit that would drive that line
The current source is the ±12 V square wave generator, with the 1.0 kΩ resistor in series, in the EVSE.
 
I know some people that deal with EV chargers a lot, and they say that unfortunately a shorted J1772 diode is quite unlikely. Perhaps they would say that, since they charge money for repaired chargers. But even if the chances of success are low, it's such a relatively low effort thing to try, that it remains quite popular.
While it is true they can fail in either mode, it has been my experience that open failure is much more likely than shorted failure. This observation is from stuff other than these chargers, but I think it is due to how the failure takes place.
fail open burns the conducting bridge, often caused by excessive heat (current) failed. failed shorted has to arc across causing an electrical path (often by exceeding the voltage limit).
Both are possible and do happen, but the 1st is much more common in my experience, again talking in general and not this one application in the charger circuit..
edit:
put another way the 1st is a failure of the conducting aspect, the 2nd a failure of the insulating aspect. it is conducting that causes heat and so is the more likely to fail. That is why you see a voltage drop across a semi conductor, and why it gets hot.
 
I know some people that deal with EV chargers a lot, and they say that unfortunately a shorted J1772 diode is quite unlikely.
From my experience in reverse engineering and troubleshooting failed OBC over the years i would agree this is quite unlikely. Most failures occur in the AC Input or in the High Voltage DC sections.

i think a DVM could be used to evaluate the presence, absence (blown), or shorting of the J1772 diode using both the resistance and diode check functions of the meter.

Referring to Davide's drawing of the J1772 found on wiki, Davide's diagram with a blown up section of it shown here

Screenshot 2024-06-21 at 11.52.38 AM.png


You would use the diode check function on pins 3 [center bottom] and 4 [lower left] looking in to the vehicle's J1772 port.

1. Red or Positive lead in socket 4 and Black or Negative in socket 3 [forward biased diode]
diode present: reading of about 1.3V or more
diode blown open: no voltage reading
diode blown short: reading of about 1V

2. Reverse or swap the polarity of the test leads connection [reversed biased diode]
diode present: no voltage reading (diode blocks)
diode blown: no voltage reading
diode short: reading of about 1 V

3. Using the Resistance function with leads as in 1.
diode present: reading of about 1.5 Meg Ohms
diode blown: no reading, OL or open circuit display
diode short: reading of about 2k Ohms

4. Resistance with leads reversed as in 2.
diode present: no reading, OL or open circuit
diode blown: no reading, OL or open circuit display
diode short: reading of about 2k Ohms.

i might recommend to try these checks before cutting any wires in the J1772 handle of your EVSE.

i made these measurements just now on my nearest EV (meiv) and using resistors and diodes on the bench (don't have a failed car to test), but maybe someone with a laef could try this also and report some helpful readings?
 
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i might recommend to try these checks before cutting any wires in the J1772 handle of your EVSE.
The best place to insert the diode in the rare case that it would help would be in the car, since that will fix the problem for public AC charging as well. If you only ever AC charge at home with that one EVSE, then you could put the diode in the handle or even inside the EVSE case. Either of these last two might cause problems charging other EVs, since the voltages will be off by another diode drop.

Ooh, I just thought about CCS fast charging, which puts control communications over the control pilot. So this diode hack will likely not work with vehicles other than Leafs and iMievs. The diode hack probably wont work even with these brands if they have a CHAdeMO to CCS conversion done.

They call this Power Line Communication, so for a long time I assumed that this was on the one or both of the live wires. But recently I found that it happens on the control pilot:

1719136579055.png
The communications signal is presumably fairly low amplitude, which means it might not get past the diode with this diode hack. Even if it does get through the diode, it will probably be distorted and reduced in amplitude, probably causing unreliable communications.

Leafs or iMiEVs with a CCS to CHAdeMO adapter should be OK with the diode in the vehicle or in the EVSE. If located in the EVSE, it won't interfere with DC charging at all, obviously. If the diode is added in the vehicle, it will be after the adapter has done the PLC injection or reading.
 
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