How can I fix a Maytag refrigerator's compressor not stopping?

Our Maytag side-by-side refrigerator MSB2154ARW is over 10 years old. It has been working flawlessly, but then lately there was water leaking on the floor. Freezer and fresh food section were cooling fine.
First Repairman checked it and added refrigerant, cleaning it at the back (where compressor and fan are). The temperature controls do not make any change in the operation times of the refrigerator.
Now, the compressor keeps working most of the time, seven and a half hours straight and then only stopping for the defrost cycle for about 25 minutes and then again running for another seven hours. There is ice building up on the coils close to the fan and the one close to the compressor.
The second repairman on his first visit adjusted the pressure of the refrigerant (result: not change at all on the cycle described) and then on his second visit said the problem was the temperature control assembly that we have now already replaced with an original part without change on the compressor cycle described.
No matter what position you use for the temperature settings (1, 5 or 9) the compressor will only stop on the defrost cycle after seven and a half hours running.