I have a 98 Ram 1500, 4WD, 5.9L. I lose all the freon due to a leaky part under the dash with the heater core. The dye test leaks on the underside but said I'd need to take out the dash to replace the part. Anyone know what that part is? It's been 3 years since I had it looked at, so I don't have the paper with the notes on it.

 

Evaporator Core. And yep, gotta pull the dash to change it. While you are in there, change the heater core too.