friend from Venezuela, if you're an electrical technician you have a good resource to undertake air conditioner and refrigeration repairs, start experiencing with your equipment and read about regrigeration theory and you'll do the practice with us. ola amigo de Venezuela, si eres electricista tienes un buen recurso para emprender en reparaciones de aire acondicionado y refrigeraci?n,comienza experimentando en tu equipo y lee sobre la teoria de refrigeraci?n que la pr?ctica la haces con nosotros.I answer you, these small equipments don't have high or low pressure sensor.The symptom that you describe is most commonly refrigerant leakage, that you must check with a manometer. In the service pump you must insert a puncture valve,connect it to the manifold through a blue cooling hose on the low pressure gauge. Insert the alex key on the puncture valve and rotate it to penetrate the tip and break the pipe, then rotate in the opposite direction so the regrigerant gets to the manometer and the low pressure can be measured, which in a regular state should be 60 PSI while the air conditioner is onTo freeze, the evaporator must be at 10 or 20 poundsIf that's the situation, you must find the leak and weld it with autogenousthen you will have to vacuum, with a vacuum pump for about five minutesWithout air getting in, supply the R22 refrigerant, you'll have to buy a Kg and charge until the manometer gets to 60 PSI, at this moment, the return or suction of the compressor will sweatIf you can seal the hole of the puncture valve, do it, otherwise, close it and leave it stuck.As you may realize, the repairing process ain't so simple and if you don't have the tools, it will be more economic to entrust the repair to a specialized service centerI hope my appreciation helps you