Downtime is expensive. When your chiller throws an alarm or stops cooling, every minute counts. Here are the eight most common industrial chiller problems we see — and how to fix them fast.

The good news: 80% of emergency service calls are preventable with a basic quarterly preventive maintenance program. The even better news — most of these issues can be diagnosed and resolved without waiting for a service technician.

1. Low Refrigerant Charge

Symptoms: Poor cooling performance, high head pressure, compressor running but not delivering setpoint temperatures, suction pressure lower than normal.

Root cause: A refrigerant leak somewhere in the system — most commonly at fittings, Schrader valve cores, brazed joints, or the evaporator coil.

Fix: Leak test the entire system (electronic detector, nitrogen pressure test, or UV dye). Locate and repair the leak. Pull a vacuum to 500 microns. Weigh in the correct refrigerant charge per the nameplate. Never just "top off" a leaking system — fix the source first.

2. Dirty or Blocked Condenser Coils

Symptoms: High head pressure alarms, compressor cycling on high-pressure cutout, reduced cooling capacity, higher-than-normal discharge temperatures.

Root cause: Dust, dirt, cottonwood seeds, or debris accumulating on air-cooled condenser coils restricts airflow and reduces heat rejection efficiency. Very common in outdoor installations or dusty industrial environments.

Fix: Chemical clean or pressure-wash coils from the inside out (blowing debris out the way it came in). Schedule coil cleaning at least once per year — twice per year in dusty environments or where cottonwood is present.

3. Failed Condenser Fan Motor

Symptoms: Air-cooled unit overheating, high head pressure, tripped high-pressure switch, one fan deck not spinning.

Root cause: Motor bearing failure, capacitor failure (common on single-phase motors), or overheating due to restricted airflow from dirty coils.

Fix: Replace the failed motor. If the compressor tripped, let the unit cool before restarting. Keep spare condenser fan motors for your specific chiller models on-site — a failed motor is a <1 hour fix with a spare in hand, versus a multi-day wait for a part.

4. Fouled Evaporator Tubes

Symptoms: Low suction pressure, leaving water temperature above setpoint, evaporator approaching freeze-up temperatures, reduced flow.

Root cause: Scale, biofilm, or mineral deposits on evaporator heat transfer surfaces — usually the result of inadequate water treatment on water-cooled systems.

Fix: Brush-clean or acid-wash evaporator tubes. Implement a water treatment program to prevent recurrence. Schedule evaporator tube cleaning every 2–3 years as part of preventive maintenance.

5. Water Flow Issues (Low Flow Switch Trip)

Symptoms: "Low flow" alarm, chiller shuts down on flow switch, freeze protection active.

Root cause: Clogged Y-strainer (the most common cause), closed isolation valve, failed pump, or air trapped in the system.

Fix: Check and clean the Y-strainer first — this fixes 70% of low-flow alarms. Verify all isolation valves are open. If the pump is running but flow is low, check impeller condition. Clean the Y-strainer monthly as part of routine PM.

6. Oil Pressure Fault (Screw Chillers)

Symptoms: Oil pressure low alarm on screw-type chillers, compressor protection shutdown.

Root cause: Clogged oil filter (most common), failed oil pump, oil separator issues, or a faulty oil pressure sensor.

Fix: Change the oil filter — this should be done twice per year regardless. If the filter is clean, test the oil pressure sensor directly. A failed sensor is a cheap and quick fix; confirm before condemning the oil pump.

7. High Discharge Temperature

Symptoms: High discharge temperature alarm, potential compressor overtemp protection trip, abnormally hot discharge line to the touch.

Root cause: Overcharged system, non-condensables (air or nitrogen) in the refrigerant circuit, or dirty condenser coils (see #2).

Fix: If coils are clean and airflow is unrestricted, recover the refrigerant charge, pull the system to a deep vacuum (500 microns or lower to remove non-condensables), and weigh in the correct charge per the nameplate.

8. Control Board or Sensor Failure

Symptoms: Intermittent or random alarms with no clear refrigerant-side cause, erratic temperature readings, phantom fault codes.

Root cause: Failed temperature or pressure sensor (most common), loose wiring connection, or controller board failure. Sensors are consumable items that degrade over time.

Fix: Most sensors swap in under 15 minutes with the right replacement on hand. Keep critical sensors (suction/discharge pressure transducers, leaving water temperature sensor) in your spare parts inventory for your chiller model. Board replacement requires a qualified technician.

Pro tip: 80% of emergency chiller calls are preventable with a quarterly preventive maintenance program that includes coil inspection, strainer cleaning, refrigerant pressure check, and electrical inspection. An annual service by a qualified technician catches what quarterly checks miss.

Questions about a specific alarm code? Call Rite-Temp at 1.800.462.3120 and describe the fault — our team can often diagnose the cause over the phone.