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BuildingWrench repair guide

HVAC

Rooftop Unit Not Cooling? Safe Checks Before Calling HVAC Service

Maintenance can safely verify thermostat demand, schedules, filters, airflow, visible disconnect status, obvious alarms, and condensate problems before handing compressor or electrical diagnosis to HVAC service.

Last reviewed 2026-09-12 · General facility-maintenance information, not a substitute for site procedures, manufacturer instructions, codes, or qualified professional judgment.

Diagnose then escalateSkill: Beginner-friendlyFormat: Diagnose → Fix → Test
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Quick answer

When an RTU is not cooling, confirm that the building is actually calling for cooling before assuming a refrigeration failure. Check schedules, thermostat demand, filters, airflow, obvious alarms, and condensate safeties, then document what the unit is doing.

Safety boundary

Do not bypass safeties, open refrigerant circuits, or perform energized electrical diagnosis unless trained and authorized.

Full troubleshooting steps are in Pro

The safety boundary, quick answer and stop-work conditions above stay free. Pro opens the likely causes, symptom table, step-by-step procedure and preventive maintenance for this guide.

Stop and call a licensed professional when

  • Burning odor or abnormal electrical noise
  • Repeated breaker or fault trips
  • Refrigerant work is suspected
  • Roof access is unsafe

Mistakes, FAQ, parts and tools

Pro opens the rest of this guide: common mistakes, field FAQ, the parts list, and the tools for the job.

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