The amount of heat and the rate at which it transfers depends upon the temperature difference between the outside air and the refrigerant. The lower the temperature of the outside air, the more cooling is done by the heat exchanger, instead of the compressor. When the outside air temperature increases, the air-conditioner works harder to cool your rig because the compressor load is forced to increase.
All air conditioners are forced to work harder as outside temperatures increase because the air conditioning cycle requires the outside temps to be lower than the heat being released from the unit.
Understanding your AC Units Cooling Cycle
Air conditioners operate in a continuous cycle that involves compression, condensation, expansion and evaporation. Inside the unit, the air conditioner compresses the gaseous refrigerant, which increases its temperature. A fan blows outside air across the unit’s coils containing the hot, high-pressure refrigerant. When the outside air is cooler than the fluid, heat energy flows from the refrigerant to the outside air. When the high temperature gaseous refrigerant gives up energy, it turns back into a liquid.
The high-temperature, high-pressure liquid goes through an expander, which converts the refrigerant to a low-temperature, low-pressure liquid as it enters the inside of your rig. There interior fan blows inside air across the coils, where the warmer air sends heat into the cool coils, converting the liquid to a gas. The gaseous refrigerant enters the compressor and the cycle starts again.
Note: An air conditioning cycle involves the circulation of a refrigerant that transitions to a gas or vapor that absorbs heat from the desired location and transfers it outdoors.