Ok was 89 degrees outside and i worked in it all day driveing home from work i had the ac on and was feeling good so i stoped by the local touchless car wash payed my 6 bucks and drove in. takes about 4 min to complete left the truck running and ac cranked. came out and pulled by the vancum to suck up the carpet when i was removeing the passager side floor mat i seen a 50 cent piece size of puddled antifreeze on the mat i looked up under the dash and cant seem to find were it is leaking from i washed the mat put it back in and drove around and no puddle. any one have any clue?

 

sounds heater core related to me.....but usually they drain outside under the passenger, side not inside.
I would take it in and have it pressure tested