AC only works on high speed 3&4 but not 1&2

First thing I would check is the AC condenser blower resistor module - either test it or replace it and see if it helps. It varies by year and engine; 971281M000 - 2.0/2.4L Theta II, 971792J000 - 2010-15, 971791F200 / 971791F210 - 2005-10 (check first, it's probably J000 or M000). Check for dirty contacts here, and if you can spray the connectors on both sides with contact cleaner, you can avoid the parts cost but don't expect a miracle either. It's typically located under the passenger side of the dashboard, mounted into the side of the plastic heater box but that's also why I linked the SM. The automatic one (M000) is a replace only part, it can’t be cleaned unless it’s just the connector.

Ran into this on a GMT800 years ago, but this should still be relevant. A lot of these modules use wiper blade contacts, so they wear with time as you use the controls. What you can sometimes do to repair them is to take the module out of the dash, take it apart and then if it moves one hard notch at a time, it uses a wiper resistor design but if you turn it and it spins constantly it uses a potentiometer. The potentiometer type can be recovered too, but a lot more disassembly is required and you need to get it in the gap so it creeps in. The wiper resistor models need to be taken apart, cleaned with a microfiber and reassembled and if you can do it, add die electric grease to protect it in the future. SM can be found here: https://www.allcarmanuals.com/factory-se...

In the event the module is too far gone, the Hyundai/Kia P/N is: 97250-3W021 OR 97250-3W130BLH (2011-13), 97250-3W220 OR 97250-3WXXX (2014-2016).

This isn't for a car but I tagged the step which shows where to get it in the permalink: ボリュームコントロールポテンショメータの清掃 -- skip the dealer if you can, but you want to use a reputable supplier. I've used Kiapartsnow more than once and I've always gotten the real deal. NOW THAT SAID for things like harnesses and such that can be aftermarket I see no reason not to weigh it but don't do that for crucial parts. I use CRC QD for price reasons but it’s also automotive safe for about the same money as the Deoxit product. HyundaiPartsDeal might be of use too.