The fault with your charger might be a bit different to the ones I am working on. It sounds like DC-DC is still working which means the 20 amp fuse has not been blown. It also seems to detect when AC is connected.
"The apparent diagnosis: when I plug my charging cable, the green charging light on the cable box comes on for several seconds, I hear a
few clicks to the cable and to the car, the car's blower starts a few seconds, then everything stops, no blower, no green light on the cable,
and no fault on the cable or on the dashboard."
With the ignition key closed, when I take the voltage across the auxiliary battery, I get 12.4 volts
With the ignition key open, I get 14.5 volts."
The input to your on board charrger is working as the AC is being detected, since you hear the contactors and blower come on for a bit.
It sounds like the DC-DC Converter section is also working as you see the voltage on the 12v aux go from 12.4 to 14.5, but not sure when you say "key open" and "key closed" seems to be opposite. When the car is "READY" you should see the higher voltage of 14+ volts which means the DC-DC Converter is charging the battery. When the car is OFF, The 12V Aux battery voltage should drop down to the 12v range.
"Do I have to believe that the 360/12 VDC converter works?"
Based on the above, it does look like the DC-DC 360/12 part of the box is working
"Anyway, the problem is that I can not do without my "Z", how to do if the repair is worse than the load on the Chademo terminal?
Just confirming, you earlier said you can still use the Chademo charger at IKEA with no problems? If so, that goes through a seperate relay and contactors and fuse, so that should be mostly separate to faults with the on board charger.
If you remove the Charrger/dc-dc converter out of the car, you would need to do a few things to be able to use the car while working on the charrger:
1) The liquid coolant runs in series from tank to pump to MCU (motor control unit) To Charrger, and back to pump.
with the charrger removed, you would need to put a bit of pipe between the hose that is the charrger coolant IN to the charrger coolant OUT of the charrger, so that a bypass is made and the full loop is present. If this is not done, the coolant will not flow and cool the MCU.
2) With the charrger out of the car, The 12v aux battery will not get charged and will continue to drain. you could connect an external 12v battery charrger to the battery every night, so you could do a few small drives during the day, and then put back on the external 12v charrger again every night.
3) You could still charge the car at IKEA CHADEMO to maintain power in the 360v traction battery.
"Can I remove the PCB from the charrger for repair and continue charging with the Chademo plug?"
And does the accessory battery continue to charge?
The connection of the traction battery goes through the charrger pcb, then goes down to the lower pcb that is the DC-DC Converter.
There is also some communications lines that go from top section down to bottom DC-DC section.
It might be possible to do some kind of bypass connections but its not really easy.
It's probably easier to use an external 12v charrger every night as long as your not using the car for long trips, and use the CHADEMO at IKEA to keep charge on the traction battery while you have the whole box out of the car. You would still need to bypass the coolant hoses so the MCU still has coolant circulated ok.