I Have a BPL frost free refrigerator which works freezes continuously after certain temp it has to stop it does not stop

You need to unplug the defrost timer and replace it with one that matches your unit. This timer is found either next to the thermostat and has a one-way plastic screw slot so you can turn it clockwise only. The timer can also be located under the unit. You can test it by turning until it clicks and the compressor turns off along with freezer fan. At that time the defrost heater should come on that is located on the freezer coils and you should be able to hear it and see water coming out of condensate drain. It could also be that your heater is bad because they usually go out before the timer and need replacing along with the defrost terminator t-stat wired next to and in series to heater. It's a round "button" type t-stat clamped to the coils. Be very careful not to bend any tubing when replacing this t-stat and heater. You need to also make sure you clean the coils under the unit along with the condenser fan with spray soap and water (a water hose nozzle works best). Some units do not have coils and a fan under the unit, but just coils on the back.