HVAC

BuildingWrench repair guide

HVAC

HVAC Short Cycling: What Maintenance Can Document Before Service

Short cycling means equipment starts and stops more frequently than expected. Time the cycles and record thermostat demand, airflow, faults, and weather rather than repeatedly resetting the unit.

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

Routine facility fixSkill: Beginner-friendlyFormat: Diagnose → Fix → Test
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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

  • Breakers or overloads trip
  • Compressor cycles rapidly
  • Electrical or refrigerant testing is required
  • Burning smell occurs

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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HVAC

Rooftop Unit Not Cooling? Safe Checks Before Calling HVAC Service

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.

HVAC

HVAC Evaporator Coil Frozen: What to Do Before It Becomes a Bigger Problem

Ice on an evaporator coil is a symptom. Low airflow, dirty filters, fan problems, blocked coils, controls, or refrigerant conditions can all contribute. Stop cooling and let the coil thaw naturally.

HVAC

RTU Fan Runs but No Cold Air: What Maintenance Should Check

If the rooftop fan runs but supply air is not cooling, the airflow circuit is alive but the cooling stage may be locked out, not commanded, or unable to operate. Gather evidence before calling service.

HVAC

HVAC Problem: General Triage for Any Complaint

Sort the complaint into temperature, airflow, humidity, water, or noise. Each has a short list of routine checks facility staff can do: schedules and setpoints, filters, dampers and returns, condensate, and outdoor-unit clearance. Refrigerant, gas, combustion, and energized electrical work is licensed-technician work.