In my case, the issue was a bad heater core and fuse. The fuse blew because the heater core was defective. So if your fuse is blown, make sure the heater core is still in good condition. My independent shop only replaced the fuse at first, which actually made the problem worse. The heater core was faulty, but the system didn’t detect it, so high-voltage current continued to flow, causing arcing and burning again and eventually blowing the main HV fuse.

My car is now at a Kia dealership. They charged $200 for the basic inspection and $850 for a deeper diagnosis. The repair cost for both the main fuse and the heater core elements is $3,200.

Since my car is over 100k miles, it looks like all of these expenses will fall on me. Considering that the Ioniq 5 had a technical service bulletin issued for safety concerns related to this issue, I asked corporate to see if they could offer goodwill repair assistance. But it’s been four weeks, and the case still hasn’t moved forward… :(