Bought the fridge used. First time plugged in it took 24 hours to get freezer down to 0 and fridge down to 40. About a week later, freezer was creeping up to 10 and fridge about 45. I unplugged the fridge thinking the coils were frosted up or back/underneath needed cleaning. Did not remove back of freezer because of all the dismantling that is involved. Left unplugged for 24 hours, plugged in and took about 24 hours to get to 0 and 40 and ran great for about a week. Temps increased to 15/50. Unplugged, let sit in case coils were frosted up and began to remove freezer parts and ice maker. After much procrastination on my part, about 24 hours, I finally finished dismantling the freezer. At that time, I found water in bottom of freezer and water on floor leaking out from under fridge. Changed defrost timer and fridge wouldn't run at all. Fans worked, electrical worked but fridge wouldn't cool. Had a repairman come, he changed the setting on the defrost timer and fridge kicked on but he said the defrost heater tested as being bad. He was going to replace but he said now he thinks I have a refrigerant leak/problem because the coils don't frost up right away when we plug the fridge in. The bottom third frost up in about 15-20 minutes. 1 hour later, half the coils are frosted. 2 hours later 3/4 the coils were frosted. He doesn't think this is functioning properly even though my fridge clearly says it takes 24 hours to get to correct temp. Does it truly sound like I have a refrigerant problem or should I try replacing the defrost heater and see if the fridge runs well?