If it fails: the first hour
What the site contact should do before the technician arrives.
- Check the thermostat setting and breaker before assuming equipment failure
- Note which zones or areas are affected if the building has multiple units
- Move sensitive inventory or equipment away from extreme temperature areas
- Call the HVAC provider with the unit type, tonnage if known, and the specific symptom
What fails
What a service call includes
- Diagnostic check of refrigerant charge, electrical components and airflow to identify the actual failure
- Testing contactors, capacitors and relays under load, not just visual inspection
- Checking condenser and evaporator coil condition and cleaning if fouling is contributing to the failure
- Clearing the condensate drain line and testing the float switch
- Verifying economizer damper operation and outside air control
- Checking refrigerant charge against manufacturer specification and leak-testing if charge is low
- Restoring the unit to proper operation and confirming supply air temperature is within range
- Written report noting the failure cause and any additional deficiencies observed
Preventive checklist
The items a maintenance program should carry for this system. Build a combined checklist across systems with the checklist builder.
Spring
- Pre-cooling season check of refrigerant charge and condenser coil condition
- Test economizer operation before high cooling demand starts
- Clean condensate drain lines before humid season
Fall
- Pre-heating season check of heat exchanger, ignition and gas components
- Inspect belts and blower motor bearings before heavy heating runtime
Quarterly
- Change or check air filters and inspect for restricted airflow
- Visual check of electrical components for signs of wear
Annual
- Full system inspection including refrigerant charge, electrical, controls and coil condition
- Combustion analysis on gas heating components
- Review unit age and condition against expected service life for replacement planning
What it costs
| item | typical range | what moves it |
|---|---|---|
| Diagnostic service call | $150 to $350 | Often credited toward the repair if performed by the same provider |
| Contactor or capacitor replacement | $200 to $500 | Relatively low-cost fix for a common no-cool call |
| Refrigerant leak repair and recharge | $400 to $2,500 | Depends on leak location, refrigerant type, and unit accessibility |
| Compressor replacement | $2,000 to $6,000 | Unit tonnage and whether the compressor is still under manufacturer warranty |
| Blower motor replacement | $500 to $1,800 | Motor horsepower and whether it is a direct-drive or belt-drive unit |
National ranges. Local labor, access, after-hours timing and materials move them. Multi-site programs usually price below one-off calls.
When this is an emergency
Complete loss of heating or cooling during extreme weather, or a unit that will not shut off and is running continuously.
How to choose a provider
- Ask whether the technician is licensed and EPA certified to handle refrigerant on the specific system type installed
- Confirm the provider stocks common parts for the unit brand to avoid multi-day delays waiting on shipping
- Ask whether diagnostic fees are credited toward the repair cost
- Check whether they offer a preventive maintenance contract to reduce future emergency calls
- Ask how quickly they can respond for no-heat or no-cool emergencies
Questions
Why does a rooftop unit keep tripping the breaker?
Usually a failing compressor drawing excess current, a shorted electrical component, or a severely restricted airflow condition causing the compressor to overheat. A technician needs to test under load to isolate the cause.
Is it worth repairing an older rooftop unit?
Depends on the unit's age and the cost of the repair relative to replacement. A unit past 15 years with a major compressor failure is often a better candidate for replacement than repair.
How fast can a no-cool call typically be resolved?
A straightforward electrical component failure can often be fixed same day. A refrigerant leak or compressor failure can take longer due to parts availability.
What is the most common cause of a commercial AC not cooling?
A dirty condenser coil restricting airflow and raising head pressure, or a low refrigerant charge from a slow leak, are the two most frequent causes.