I have a Frigidaire refrigerator only that runs continuously. The defrost timer and thermostat have been replaced. It gets down to 37-38 degrees but never shuts off until the thermostat is turned down to just about 1 on the dial or the defrost time goes into defrost. Even when the thermostat is turned to the coldest position it doesn't seem to get much colder. Could this be caused by low refrigerant?

Thanks for the reply Richappy,
This just a refrigerator only. The matching freezer is a seperate unit.

When this refrigerator was about 1 yr. old it wouldn't cool properly. It was found to have a leak in the evaporator. This was repaired under warranty and has worked great for about 3-4 yrs. This time when it quit working I called the company that repaired it under warranty but they no longer work on refrigerators. Another local company came out, was here about 10 minutes, told my wife the problem was in the evap system and would be $1200-$1300 dollars to repair. We paid $700 for it new! I found a similar problem on this forum telling how to diagnose the problem. Evaporator fan runs fine. I found ice build up on one end of the evaporator. I forced the defrost timer, it went into defrost, problem solved. I installed new timer, everything seemed OK. We noticed the only time it shut down after this was when the 12hr.timer went into defrost. I noticed using a digital temp meter it only got down to about 36F. no matter the dial setting so I replaced the thermostat. Now I still have the same problem, runs continuously, 36-37F no matter the dial setting and after pulling the cover found quite a bit of ice on the evaporator. Whew! long story. Thanks for your patience. Condensor is clean and fan works good.