[bowman1964]

|PuNiSh3R| i am not positive but your problem with the up and down temps is proberly the condensor.a dd cube as you are using if my memory serves me right doent have the tubes properly running to use in refridgeration system.you see if the freon when cooled at the the first part of the condensor starts to liqiidfiy it will collect in the low spots in the tube bends.and i have found that is shows signs of the pressure running erractic up and down and temp movement.now this is caused by say your system is running fine and is cooling lets say at -20.now after a few minutes the freon starts to make it all the way around the system evenly.but it starts to puddle in a low spot in the condensor.which after a while will run the evaporator out of freon or stops the steady flow of liqiud to the calpillary tube.now when this happens all of a sudden there is no freon boiling off in the evap.this causes the low pressure to drop because now the compressor is sucking harder and there is no boil off to offset the hard vaccum.so temps go up suddenly.now after a short time enough freon makes it back to the condensor to push the rest out of the low spot in the condensor and the cooling starts again.

now you can check this by moving the condensor while the system is running and watch the temps.and see if i am right.
now you can add more freon to offset the low spot in the condersor but it will raise the low side pressure causing your temps to rise.
so i hope this helps..i might me wrong about the dd cube if so i am sorry but been a while since i saw one.in my hands