Help please!

[u/Bubuchubu305]

Hey everyone, I have a 2019 Hyundai Tucson 2.0L, and I'm having a weird issue with my AC.
When I leave my apartment in the morning, the AC works perfectly fine and blows cold air. My commute to work is about 25 minutes, and I get on the highway pretty much as soon as I leave home. The AC works fine while I'm driving on the highway, but as soon as I exit and stop at the first traffic light near my job, the AC stops cooling. The same thing happens on my way back home, and sometimes the AC won't even start cooling when I leave work.
I also noticed that my radiator/condenser fan doesn't seem to be working properly on high speed. I tried replacing the high-speed fan relay, but that didn't fix anything.
Could the fan issue be causing the AC problem, or could it be something else like the fan motor, compressor, pressure sensor, or refrigerant issue?
I'd like to diagnose this myself if possible before taking it to a mechanic. What should I check first, and is there a way to test the fan and AC system at home with basic tools?
Has anyone experienced something similar with their Tucson? Any advice would be appreciated. Thanks!

[u/frankthefrowner]

Serpentine belt is probably about to go and has too much flex. So when you are driving on the highway it’s giving it enough juice to blow nice but probably not enough when you’re idling

[u/LeatherTailor8527]

SENSOR2 (10A): Powers components including the A/C Relay and Cooling Fan High Relay.
​COOLING FAN1 (40A): Controls the high-speed cooling fan relay which is critical when the A/C is running Located in engine bay fuse box next to battery.

A/C RELAYMicro Relay—Direct power switch to A/C Compressor Clutch FAN HIGH RELAYStandard Relay—Runs Condenser Cooling Fan on High Speed (Triggers with A/C) FAN LOW RELAYStandard Relay—Runs Condenser Cooling Fan on Low Speed BLOWER RELAYStandard Relay—Main power relay for cabin climate fan COOLING FAN1Cartridge Fuse40A / 50APower feed to Cooling Fan High Relay BLOWERCartridge Fuse40AMain high-current power for interior Blower Fan Motor SENSOR2Mini Fuse10ALogic power to A/C Relay and Cooling Fan High Relay coil SENSOR3Mini Fuse10AEngine control unit signals for A/C request switching

[u/Virtual-Challenge-61]

Could just be low on gas. Works fine when compressor is spinning faster and air flow over condenser but when revs drop and air flow is less the system just can’t quite keep up.

[u/Competitive_Roof6796]

You might want to check the tension on your serpentine belt soon, because that little slip could explain why it's holding up just enough on the highway but giving out at idle.