Methods of testing used to locate the sources of trouble are based on the operating parameters or principles of the mechanism being suspected of trouble. By performing HVAC Troubleshooting and checking the pressures, the temperatures, running, etc, the serviceman is soon able to isolate or pick out that part of the system which is giving trouble.

 Of course the technician must have a thorough knowledge of the fundamentals of refrigeration and air conditioning and the cycles associated with them before he or she can become a reliable and competent troubleshooter. When beginning the troubleshooting process it is obvious that one must locate the troubled mechanism before dismantling it, in order to keep the cost of servicing at a minimum, and to make sure the repair work is going to enable proper function of the mechanism after assembly.


 Methods of locating troubles naturally vary with the type of system, that is, what type of system it is. Heat Pump, Straight AC, Split System, type of refrigerant used, direct expansion, capillary tube etc. The call for service should give the first indication of what the trouble will be. The best method of trouble tracing or shooting is best learned and is best adapted to practical work by first classifying the type of service requested; the unit is not blowing air, as an example. Some of the most generic in troubleshooting tips that a technician should follow are:

 Checking Low Side Pressures

 High Side Pressures

 Temperature of cooling unit

 Temperatures of liquid (High Side) and suction (low side) lines

 Amount of dryness in refrigerant (if available)

 Running time, like short cycles, or not running at all or even continuous run etc.

 Check for Leaks

 And finally noise.



As with any technician or company that offers periodic maintenance checks it is recommended that the following be checked at pre-determined times or intervals to prolong the life of any unit. Periodic maintenance falls under the troubleshooting criteria due to the fact that the HVAC Technician should have the applied training and knowledge to perform such tasks.



All inspections should cover such things as:

 Electrical connections

 Motor and safety devices

 Compressor noises

 Overload cut-out



 Fans and filters.

 HVAC Troubleshooting is a step by step approach at which many times you will fix one problem only to find yet another. However, I was always taught that when it comes to troubleshooting you can expect that in most cases say 85% of the time the trouble will be electrical in nature.

HVAC Troubleshooting  (A/C System) Most Common

A/C Unit Will Not Start                                                                          

No Power/Check Breakers/Burnt Wires/Faulty Thermostat

Indoor Fan running but no Air Flow                                                

Evaporator Coil Frozen/Low Charge/Dirty Air Filter

Outdoor Fan Not Working                                                                     

Bad Capacitor/Bad Motor/Burnt Wires/No Power

Outdoor Fan Runs but Compressor Doesnt                                    

*Low Charge Unit Tripped on Overload/ Bad Compressor/

Check Wiring/Bad Contactor/

*Note:  Many times if you wait approximately 15 Minutes and the unit is tripped on the overload the compressor will attempt to once again run.  If it does, this is a clear sign of an undercharge however be mindful that if there is an undercharge there is a leak and should be taken care of.  In the meantime disconnect the power source and either make repairs and/or call a technician.

Both Outdoor Fan and Compressor Not Running                          

Check Wiring/Check Power/Bad Thermostat,Contactor

Note:  It is normal to have your suction line sweating during the summer.  This is a good indication that your system (charge wise) is running adequatley.  The coolness of the refrigerant is what keeps your compressor cool.  As you lose refrigerant over time due to a leak that line will get warmer and warmer thus causing your unit to trip on what is called a thermostatic overload.  This is only just a HVAC Troubleshooting guide as there are many other different tips, tricks and charts that can be utilized however these are the home owners most common problems.