And how is that possible? Model Y is charging at a reduced current because it is not fully plugged in to the charge port. If it's not fully plugged in, how would it charge at all? Either it's plugged in or not, no? That's like being a little bit pregnant.
There's two signal leads, a ground lead, and the two power leads (the biggies). My understanding is that the longest pin is the ground, followed by the differential signal leads, followed by the mongo power leads.
I'm just hypothesizing here, but I've had to work with stuff like this for a living, sometimes. In no particular order:
- The signal leads are differential, in that one signal is going positive whilst the other is going negative; typically, these would go into some kind of rugged differential receiver with a single-ended output for use by the car's computer.
- Suppose that the ground wire isn't making contact, because of dirt/grunge/busted wires. Given that that's a differential receiver in there that probably has a decent common-mode range (i.e., the common dc offsets on the two signal leads may be non-zero), communications may be up, sorta, but there would be a distinct error in that those DC offsets aren't at zero with respect to the ground pin. No charging until that ground pin is actually grounded, so let's flash amber.
- Suppose that one of the two signal leads and the ground are making contact, but the other signal lead isn't. Well, it's a differential receiver, and let's just guess and say that the "open" wire defaults to ground, done with a resistor or something. Hence, signalling may be received, even with one signal wire open, but an activity detector on the open wire detects No Movement Today - and that's a fault. Flash the amber time.
- Going along with the grunge ideas, it's possible that the differential signal is below a required threshold, due to high resistance/broken driver/etc. Again, communications might be working, but not all that well. Flashing Amber Time.
Depending upon the SAE and its ideas about Safety Protocols Uber Alles, there may be additional checks, left, right, and center.
Ha. One Day, Back In The Deeps Of Time, I got sent to the factory to find out why this particular system that they were trying to commission kept on failing, repetitively, even when circuit boards were swapped in, out, and sideways, leading to enormous amounts of head-scratching. I showed up with an o'scope, VOM, white wires, and a soldering iron and started to troubleshoot. Weird - there the signal was on the backplane, there it wasn't on the circuit board and.. the ohmmeter said Open. No bent pins, anywhere, and the connector on the circuit board was fine and said board worked just fine on another system.
Got this blame pin-puller (factories have stuff like that) and pulled the pin. The blame thing had something that I swear looked like shellac all over it. None of the other pins had that - just
that one. Replaced the pin, everything comes back to life.
We took pictures with a microscope, called the pin manufacturer and the backplane build guys, and nobody could explain this. Weird.
Now, that was on a piece of gear that gets buried in nice, clean, central offices with air filters and all that jazz. Now you're talking about a NACS connector that's exposed to polluted air with NOx and SOx, water, humidity, dirt, bugs (I've pulled
lots of bugs out of backplanes, I know a lot about Indian sub-continent bugs these days), and what-all. I'm not kidding about the grunge on pins. Time to get out a magnifying glass and a bright light.