Water is leaking in the floorboard of my truck, especially when I make turns. I believe it is the air conditioner. What can I do to fix it?

your heater core is bad they leak when they go bad youll have to replace its under/behind the dash

no it will most likely be a blocked drain pipe that goes into the engine bay from the A/C and drains the condensation created by your car's air conditioner. A mechanic workshop can do a blast of compressed air by your mechanic and free the blockage takes about 30 seconds to do with a car hoist.
If it is humid conditions the problem will be much more and you might find the front demister won't work due to water sitting on top of the Air conditioner. It will heat this water and blow steam on your window.

Look for moisture on the glass of the windshield, as well as the passenger side door, if thebottom seal isnt making contact on the door glass water will run in threw the door

you need a new heater core

try having an assistant 'water'' your car with a garden hose while you're in it.especially check seals at windshield & doors.it could take a few minutes of ''watering'' before a leak shows up.

air conditioner

does it smell sweet, if sounds like you got a leaking heater core, sounds like to much for just condensation...

check all coolant line going to the heater core of vehicle

It is most likely leaking from the windshield and running down to the floor. Good luck and dont forget to rate

Look on the outside at the firewall (back end of engine area ) on the passenger side. Little black rubber tube sticking out, usually 90 degrees, pointing down. You need to get something up in there and clean it out, but be careful not to go too far or too hard as you don't want to poke a hole in the unit.