Before Calling Heating Cooling Repair Service - Checklist

Dirty filters commonly result in service calls.

Before Calling Heating Cooling Repair Service - Checklist – The following is a list of things you need to check before calling for heating and cooling service. Many people simply pick up the phone and call for service. When the technician arrives and finds something simple you have the sinking feeling like you could have checked it and fixed it yourself.

As a technician myself, I have responded to many service calls and found these very simple things that many homeowners can check for themselves and resolve the problem with their air conditioner or heating system. If you are uncomfortable with checking any of these things then you should call for service and let the technician check these things.

Please read the last paragraph concerning these checks and how far you should go in trying to repair your own HVAC system. Your checks should be measured and limited to this list.

Before Calling Heating Cooling Repair Service - Checklist:

Checklist before calling HVAC service

1) Check selections on the thermostat. Ensure that it is set to the desired settings. Believe it or not, I have been on service calls where someone claimed their air conditioner or heating system was not working only to find they did not have the correct setting on the thermostat. Some people did not have the selector switch set to heating or cooling or they did not have the correct set point set for the desired temperature.

Always double check the thermostat settings to make sure you set it correctly and that the heating or cooling selector switch is set properly. If the thermostat has no display see our No Display Thermostat article for troubleshooting. It happens more than you think so double check the thermostat.

Clean Filters | Before Calling Heating Cooling Repair Service

2) Always make sure you have a clean air filter. Yes, I have been on many service calls where the only problem was a dirty filter in the system. Once the dirty filter was changed the system operated normally. Keep those filters clean and free of debris and dirt.

Power Supply or Switches/Breakers | Before Calling Heating Cooling Repair Service

3) Check the power supply. This can include a circuit breaker and or/a regular-looking wall switch close to the unit. Sometimes people can mistake these switches for a light switch. By code, the switch plate should be clearly marked (usually it is red with warning letters) but sometimes these switch plates get changed for one reason or another with a regular switch plate and it is mistaken for a light switch.

Make sure this switch (if it is a standard wall light switch) is clearly marked for the heating and cooling system. Also by code, these switches should be near the indoor unit. Sometimes the indoor unit is near a door to the garage or closet and people mistake the switch for a light switch.

Lastly, most outdoor units have a disconnect switch, and sometimes the switch is like a breaker, and sometimes it is fused. These are special fuses so if you find a blown fuse make sure you replace it with a like fuse (slow-blow). An exact replacement is always desired when replacing any electrical fuse.

Fuel Supply | Before Calling Heating Cooling Repair Service

4) If the problem is heating and you have a gas furnace check to make sure the gas service has not been terminated. Sometimes the gas company will turn off the gas service because they detected a leak. They will, without notice, turn off the gas supply. Check the meter for a red tag or a lock on the gas valve leading to the meter.

Pilot Lights | Before Calling Heating Cooling Repair Service

5) If it is an older gas furnace (even water heater) check to make sure the pilot light is lit. Since most people have electronic ignition this will not be a concern but there are still gas furnaces that have pilot lights.

6) Newer gas furnaces that have electronic ignition will typically have some flash codes if something is wrong. There are also normal flash codes so be aware of that. The panel on the gas furnace should have an explanation of the flash codes so you will know if it is normal or not.

Typically, if the electronic ignition system has a diagnostic flash code that indicates a problem you need to have a qualified technician take care of the problem for you.

Ice or Freezing Equipment or Pipes

7) Check for freezing up of units. If you see any ice, turn it off. Check the filter(s) and supply vents to make sure they are open and not obstructed in any way. If you find no problems leave the unit turned off and call a service company.

You have one of two problems - low air flow across the evaporator or a refrigerant leak. If it is a leak the repair can possibly be made as soon as the service technician arrives but it depends on the severity of the leak and what can be done to fix the refrigerant leak.

HVAC Checklist

Panel Switches

8) Almost all air handlers have panel switches. Panels switches are safety switches that ensure the power is cut off to the air handler or furnace (indoor unit) if the panel is either loose or it is removed for service. It prevents accidental shock or injury from moving parts inside the furnace/air handler.

If the panel came loose then the HVAC system will not work. Make sure the panels did not come loose for whatever reason.

Condensation Drains

9) If you have an air handler or gas furnace that inside checks of the condensation drain line and cut off switch that is usually located in the secondary pan under the unit. The secondary pan will be flooded with water if there is a problem.

This means you have a clogged condensation line and it needs to be unclogged before the system will operate normally again.  These switches prevent water damage.

Recap and Conclusion

Make sure you check:

  1. the thermostat
  2. air filter(s)
  3. power supplies (switches, breakers, fuses)
  4. fuel levels or fuel supply (gas or oil)
  5. Pilot light if your furnace or water uses a pilot light
  6. Any diagnostic flash codes
  7. Check for ice or frozen pipes
  8. Panel switches
  9. Any condensation drain cut-off switches

Again, if you are uncomfortable checking any of these things always call for service and let the technician resolve the issue for you. Sometimes there could be more than one problem even if you find any of the above issues. For example, a blown fuse could be the result of a failed electrical device that needs to be repaired or replaced. These are out of the scope of most homeowners ability to repair not only from a technical perspective but also from a safety perspective.


I have found that some homeowners who went too far in trying to repair their own system ended doing more damage to the system than if they would have waited for a technician. In a few circumstances, the homeowner put themselves and others in danger because of trying to repair something themselves. So your checks should be measured and limited to your comfort level in the list above. Anything outside of that needs to be taken care of by a trained professional. Good Luck!!

High Performance HVAC

Before Calling Heating Cooling Repair Service - Checklist