Radiator fan relay
Pop open the lid to the relay and fuse center, should be an imprint of fuse/relay layout. If not, consult your owner's manual, I assume it being a 2015 you still have one.
They should have a recall on the fan's failure. I have 57,000 mileage and sometimes fan stops or doesnt turn fast... same thing on my friend's Ram Promaster city exact sam vehicle he has less than 30,000. And I see plenty of complaints about the same exact issue online... RECALL RAM PROMASTER CITY OVERHEATING DUE TO RADIATOR FAN FAILURE!
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