Before delving into the mechanisms of your portable air conditioning unit (PAC), consider doing the following: make sure there are no large obstructions situated in front of your PAC that could hinder air flow into the unit. Check the exhaust hose and remove any obstructions inside the hose, and keep the hose unbent. Lightly vacuum the evaporator and condensing coils to remove any potential clogs. If the evaporator is frosted over, allow it to defrost before resuming operation. If you own a reverse-cycle PAC unit, make sure the unit is set on the cooling mode. The set temperature should be below room temperature. If your unit is set to Auto Mode and you desire cooler temperatures, switch it to Cool Mode and key in your desired temperature.
If doing the above does not remedy the situation, then the problem is most likely caused by faulty mechanisms. The fan motor may be blown, the compressor may be malfunctioning, the coolant may have run out, etc. If your fan motor does not work any longer and you do not want to hire a professional, it is possible to change motors by yourself. Find the motor that matches your PAC model, and then follow this guide to replace your broken fan motor. If you discover that your fan motor is down, you should replace it as soon as possible as it may burn out the compressor.
If the problem lies with the compressor, chances are that the compressor is seized and is pulling on locked motor amperage until the compressor trips on internal overload. The only solution that deals with a malfunctioning compressor is buying a new one and replacing it, but as compressors usually cost two-thirds of a whole PAC unit, you might want to consider simply selling your old PAC unit to salvage places or dumping it out and purchasing a whole new unit. If the compressor is not working due to a blocked/damaged compressor-condensing coil or a broken cooling fan, either replace the component(s) or switch out your unit for a new one as those scenarios may eventually lead to overheating.
If your PAC has run out of refrigerant/coolant, simply add some into the unit. Look for a valve that is usually located on the suction side of the unit, where gauges are hooked up and show readings for the system. Make sure the refrigerant you use is the one your unit needs. Here are the steps necessary for recharging your PAC through adding refrigerant (scroll down to find the section titled ‘Method 4 of 4’). Note that refrigerants are often costly, and if you do not want to spend money on refrigerant you may simply choose to purchase a whole new unit instead.
If you have tried all the possible solutions listed above and your PAC unit is still not working, you could either call in an electrician or purchase a new PAC unit – compare cost and time required before deciding.