Repair Library

18 guides

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No Cooling: Full Troubleshooting Guide

Confirm the call for cooling at the thermostat, confirm the unit has power and is not locked out on a safety, then check the two things that cause most no-cooling calls: a loaded filter and a plugged condensate drain with a tripped float switch. Anything involving refrigerant, energized troubleshooting, or gas requires a licensed technician.

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.

Condensate Pump Not Working: Safe Checks Before Replacement

A condensate pump that stops moving water can shut down cooling or overflow. Check safe external power, the reservoir, float movement, and discharge tubing before replacing the pump.

RTU Economizer Damper Stuck Open: Signs and Safe Checks

An economizer stuck open can make a building humid, hot, cold, or pressurized. Maintenance can compare commanded versus visible damper position and check for obvious mechanical obstruction.

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 Condensate Drain Clogged? How to Clear a Routine Blockage

A clogged condensate drain can stop cooling, trip a float switch, overflow a pan, or stain a ceiling. If the drain and cleanout are safely accessible, remove buildup and verify that water flows freely before putting the unit back in service.

HVAC Float Switch Tripped: What It Means and How to Reset It Safely

A tripped condensate float switch is a warning, not the root cause. The right fix is to correct the drainage problem, remove standing water, confirm the line drains, and allow the safety to reset naturally rather than bypassing it.

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.

Mini-Split Leaking Water Indoors? Drain, Pan & Coil Checks

Water from a wall-mounted mini-split usually points to a condensate problem: a clogged drain, dirty pan, poor hose slope, disconnected line, frozen coil, or failed condensate pump. Start with the drain path and visible water source.

One Room Is Too Humid: Commercial HVAC Troubleshooting

High humidity in one room can come from excess outdoor air, low cooling runtime, exhaust imbalance, moisture sources, sensor error, or airflow problems. Measure temperature and relative humidity before changing setpoints.

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.

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.

Commercial Thermostat Screen Is Blank: What to Check First

A blank thermostat can mean dead batteries, lost 24-volt control power, a tripped condensate float switch, equipment power loss, or a loose thermostat face.

Thermostat Temperature Reading Is Wrong: How to Check It

A thermostat that reads several degrees off may be influenced by sunlight, wall temperature, drafts, local heat sources, remote-sensor configuration, or calibration. Verify with a good thermometer first.

Thermostat Says Cooling but Nothing Happens? Commercial HVAC Checks

If the thermostat shows a cooling call but the equipment does nothing, separate the problem into controls, airflow, and equipment response. Verify the schedule and setpoint first, then look for obvious safeties, alarms, airflow restrictions, or a unit that is not responding.

VRF One Zone Not Cooling: How to Narrow Down the Problem

When one VRF indoor unit is warm but the rest of the system is cooling, the failure pattern is the biggest clue. Start with local controls, mode conflicts, airflow, sensors, branch components, and fault codes before assuming a system-wide refrigerant problem.

Water-Source Heat Pump Not Cooling: Facilities Troubleshooting Checklist

For a water-source heat pump that runs but does not cool, verify thermostat demand, airflow, filter condition, loop-water availability, condensate safeties, and whether neighboring units are affected. Refrigerant and internal electrical diagnosis should be escalated.

Weak HVAC Airflow in One Room: Easy Things to Check

One room with weak airflow usually points to a local restriction or control issue: blocked grille, closed damper, crushed flex duct, terminal-unit problem, or furniture obstruction.