happymoose

I had the same problem after repairing my Ultimaker 2+ recently. I couldn't find any obvious short. Turned out I either got a defective heater cartridge or I damaged it during installation (probably the latter). Using a multimeter I saw that the heater had a resistance of ~1.3 ohms. That was causing it to try to draw way too much current. I ordered a replacement heater and the new one had a good resistance of ~19 ohms. I installed that one, and am back in business. So if you have the same issue and it is not a short at the heater block, try testing the resistance of the heater cartridge.