Room air conditioning is either through the window or through the wall type. They work much the same. Both usually have one double shafted motor, that works the condenser and evaporator fans. The capacity of these units is from 5,000 But/h to 24,000 But/h. One special application unit is roof mounted for travel trailers and motor homes.
Maintenance of room units involves keeping the filter and coils clean. Permanently sealed motors are normally used. If the motor has oil caps on each end no more than two drops of electric motor oil. If the filter is not kept clean this will cause the evaporator coil to become dirty. Causing low suction pressure and freezing up of the unit. Always keep the filter clean and installed properly.
Cleaning the coils consist of disassembling the unit far enough to gain access to both coils. Soaking the coils with coil cleaner “available at most hardware stores” per the cleaners instructions. Then rinsing with water avoiding the electrical components and fan motor. The small tube that is fastened to the evaporator and runs up into the electrical controls is the thermostat capillary tube. Do not kink or bend the tube and make sure it is fastened back to the evaporator securely. It senses the temperature to turn the compressor on and off. It must be in the correct place.
SAFETY PRECAUTION: before doing any work on the inside of the unit. Discharge the capacitor. They can shock you as well as ruin your volt-ohm meter. Purchase a 20,000-ohm, 2-watt resistor (about one dollar). Connect the resistor leads to the capacitor terminals to discharge it. If your capacitor has three terminals, work your way around making sure you have connected one terminal to the other two with the resistor leads till all three have been discharged to the other two.
The electrical components of these units will for the most part consist of the selector switch that you set the fan speed and fan only or cool with. The thermostat that you set the room temperature with. The capacitor or capacitors help start the motor and keep it running at the right speed under harsh conditions. The capacitor stores electricity and releases it back to the motor. Discharge any and all capacitors before touching them. They hold a charge and will shock you even if the unit is unplugged. The fan motor which turns the fans and or blower wheel. The compressor, and the compressor overload, and internal motor winding thermostat. While the unit is apart look over all the electrical connections, replace any that look burnt or discolored.
The selector switch changes the unit from high fan to low fan, or high cool to low cool etc… The power cord hooks directly to the selector switch, You can sometimes diagnose a faulty selector switch without disassembling the unit. For instance, if it is plugged into a known working plug and does nothing on any setting the switch is bad. If the compressor comes on in the cool settings, but the fan doesn't run on any setting. The fan motor is bad or the wiring to it. If everything works on one speed but not another, the switch is bad. The thermostat sets the room temperature. With the unit off you should be able to feel and hear a slight click as you turn the knob from far clockwise to far counterclockwise and then back.
The compressor consists of the motor windings, the internal motor winding thermostat (both are internal and not replaceable), compressor terminals and external overload. If the fan runs but the compressor does not work on any setting. Trace the wires going to the compressor, remove the plastic cover over the wires. Two wires will hook to the R and S terminals of the compressor and the black wire will hook to the external overload (its round like a quarter) a wire from it will hook to the C terminal of the compressor. Make sure all the wire connections are in good shape, repair any that are burnt. I have seen many wires burnt completely off of compressor terminals from age or a connection that got loose. Always put the plastic cover back over the compressor terminals before you plug it back in and turn it on. The terminal designation is as follows. The C is the common terminal and most always a black wire. The R is the run terminal is most always a red wire. The S is the start terminal and is mostly a blue or yellow wire, but will always come from the capacitor.
