Question:
I live in Phoenix, AZ. My outside unit (compressor) does not start when it is hot outside (from around 1:00pm to 8:00pm); and if it does then it shuts down soon after. It works normal during all other times. The run and kickstart caps seem to be fine. The outside fan always blowing. So what is causing it not to work properly during the peak of the heat? The unit is 5 years old and always worked fine. No freezing either during that period of time. Could it be that the “radiator like” or coil section of the compressor needs cleaning? although it did not look anymore dusty then last 5 years.? or could it be that the compressor is going out and it’s first symptom is not to work properly when it is too hot? Please help. Thanks

Reply:
Sounds like your machine is tripping a safety device called a refrigeration high pressure safety switch. If it is the culprit then the cause is varied.
Most common is that there isn’t enough air blowing freely over the condenser coil.
There are contaminants in the system such as air, this is not likely unless the machine has been repaired fairly recently.
The compressor is shutting down due to an internal safety such as high temperature or high amperage drawing.
After all is said and done you need professional assistance from a qualified and experienced A/C technician, it is highly unlikely you would be able fix this one yourself.