My duro therm 15000 btu air conditioner runs fine until set temp is reached. The unit then starts to cycle on and off about every 2 minutes.

That is normal operation, only the compressor cycles, the fan stays running to keep air circulating for better temp control. Otherwise the rear of the space could get 5 degrees warmer than the front

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THE OUTSIDE FAN MOTOR MIGHT NOT BE WORKING CAUSING THE COMPRESSOR TO GET HOT AND TRIP THE INTERNAL OVERLOAD IN THE COMPRESSOR - IF THE UNIT IS LOW IN FREON SAME RESULTS - WHEN UNIT IS FIRST TURNED ON DOES IT BLOW COLD AIR OR DOES THE AIR NOR FEEL COOL - JUST COOL AIR COULD BE LOW FREON - COLD THEN WARMS UP IS FAN PROBLEM

The best guess is that you have a bad thermostat. When the compressor shuts off it has to stay off for a long enough period of time for the low pressure high pressure to equalize. If it turns the compressor off and back on immediately it can't start against the heavy load created by these unequal pressures. If it will start every time after sitting for 10 minutes the thermostat is making it short cycle.

relay module or communication cable from t-stat issue.

Put in a 5 minute time delay. It is a two wire device in line with the contactor. Sounds like it is set to 75 turns of at 74 and repeats. The tstat should have a differential of 2 degrees as well.

Check the condensor unit. May be dusty. Clean it. If still problem replace capacitor.

ADDING FREON IS A LITTLE MORE COMPLEX AND BEST LEFT TO A PRO, YOU CAN MAKE SURE THE FAN IS OILED AND THAT THE FINS ARE CLEAN, TAKE NOTE IF YOU SEE A OILY SPOT ON THE UNIT THIS MAY BE THE SIGN OF A FREON LEAK ,, IT MIGHT BE WELDED AND RECHARGED .. THATS MORE BETTER THAN BUYING A NEW UNIT CUZ THESE AINT CHEAP ! JAY THE POOL PUMP GUY IN LONGWOOD FL

15,000 BTU stating current 18 to 20 amphs. And running amphs will be around 6.5 to 7 amphs.

a heat pump is a finely tuned machine that can be very efficient yet very frustrating at times. I could give you better advice if I were looking at the unit but hear are some things that may help. The unit has a defrost mode that cycles every 30,60,or 90 minutes. If you take the cover off of the condensing unit and near the top you will see the adjustor. unless you live in arctic or very humid cilimates, it should not be set to 30 min. Also the unit may be low on refrigerant. you can check this with a thermometer. put the therm. on the hot gas line(big one) and it should be 110 degrees hotter than the outside temp. Insulate the point of contact around the therm. and gas line. Also, your aux. heat may not be coming on to supplement the heat from the pump. i.e. the fusable link could have burned up and the heating element wouldnt be coming on(elec. models). there are too many variables and combinations of problems that could cause this.

turn your fan on the termostat to on (manual) it will continue to run untill you set it back to auto