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Troubleshooting · Applies to: Cold rooms with several evaporators · Direct expansion refrigeration system

The room gets too cold (solenoid valve does not close)

A room that gets too cold: controls that do not cut out, a solenoid valve that does not close, a stuck relay and sensors.

Last checked: Field mode: large buttons, questions first and the screen kept on.

A room that gets too cold receives refrigerant when it should not: either the controls do not cut out, or the solenoid valve does not close. Danfoss mentions voltage remaining on the coil, a damaged armature tube and dirt in the pilot orifice as causes of a solenoid valve not closing [1].

Work on the refrigerant circuit may only be carried out by certified personnel. Isolate the power before working on electrical parts and take particular care with high pressures (CO2) and flammable refrigerants (A2L and A3). Always follow the manufacturer's instructions.

Confirm the fault first

Measure the room temperature with a calibrated thermometer and compare with the setpoint and the sensor reading. Measure the voltage on the solenoid coil when the room has reached temperature, and the temperature after the valve.

📏 Measurement guide: calculate superheat and subcooling 🔢 Alarm and fault codes

Flowchart

The room gets too cold (solenoid valvedoes not close)1. When your calibrated thermometershows that the room has reached thesetpoint, is the solenoid coilde-energised?A · Likely causeThe controls do not cut out: sensor,setpoint or thermostat.NoYes2. Is it cold after the solenoid valvealthough the coil is de-energised?B · Likely causeThe solenoid valve does not close tightly:dirt in the pilot orifice, a damagedarmature tube or a worn seat.YesNoC · Likely causeThe room is cooled from outside: coldweather, an adjacent freezer room orcold air from another room, and there isno heating.The room gets too cold (solenoid valve does not close)1. When your calibrated thermometer shows that theroom has reached the setpoint, is the solenoid coilde-energised?A · Likely causeThe controls do not cut out: sensor, setpoint orthermostat.NoYes2. Is it cold after the solenoid valve although the coilis de-energised?B · Likely causeThe solenoid valve does not close tightly: dirt inthe pilot orifice, a damaged armature tube or aworn seat.YesNoC · Likely causeThe room is cooled from outside: cold weather, anadjacent freezer room or cold air from another room,and there is no heating.

Causes, most likely first

The order is approximate and based on common faults in the field. Always measure before replacing anything.

  1. 1
    Flowchart B

    The solenoid valve does not close tightly: dirt in the pilot orifice, a damaged armature tube or a worn seat.

    Remedy: Clean or replace the valve insert [1].

    🛠 How do I do it? Step by step

    Only qualified personnel may work on refrigeration and electrical systems. Follow the manufacturer's manual and local rules; the steps are guidance, not a replacement for training.

    Check a solenoid valve (liquid line or hot gas)

    A solenoid valve that does not open starves the evaporator (low pressure, warm room); one that does not close lets refrigerant through when it should not (pump-down fails, flooding, or hot gas leaking into the evaporator). Check the coil first, then the valve itself.

    1. Find out whether the valve should be open. Read in the controller or the wiring diagram when the valve is energised (for example with cooling demand, during pump-down or during hot gas defrost). Compare with what the system does right now.

      ✓ Check: You know whether the valve should be open or closed at this moment.

    2. Check that the coil gets voltage. Measure the voltage across the coil terminals when the valve should be open. Hold a steel screwdriver blade near (not touching) the top of the coil: a live coil pulls it slightly. Check that the coil voltage on its label matches the supply.

      ✓ Check: The coil has the rated voltage (label) when the valve should be open; if not, the fault is upstream: thermostat, controller output, contactor, fuse or wiring.

    3. Check the coil itself. Isolate and lock off, prove dead, and disconnect the coil. Measure its resistance and compare with the manufacturer's value; look for a burnt smell, discolouration or a cracked coil. Make sure the coil is the right type for the valve body and sits fully down on the armature tube with its nut tight.

      ✓ Check: Coil resistance matches the data (an open circuit or a very low value means a faulty coil), and the coil is the right one and correctly fitted.

    4. Check that the valve opens. With the coil energised and the system running, measure the temperature on both sides of the valve with clamp thermometers. An open valve has (almost) the same liquid temperature on both sides; a clear temperature drop or frost after the valve means it is not opening fully or is restricted. Check the flow direction arrow on the valve body.

      ✓ Check: Little or no temperature difference across the valve when it should be open, and it is fitted in the direction of the arrow.

    5. Check that the valve closes. De-energise the coil (or let the controller close it) and watch what happens: on a pump-down system the suction pressure must fall and the compressor must stop on the low pressure switch and stay off; a hot gas valve must leave the line after it cool during the freeze or cooling cycle.

      ✓ Check: The system pumps down and stays down, or the line after a hot gas valve stays cool; a valve that leaks through must be repaired or replaced.

    6. Repair or replace. A faulty coil can be changed without opening the circuit. If the valve body leaks or sticks, opening the circuit is work for certified personnel: recover the refrigerant, replace the valve (or its internal parts) with nitrogen flowing while brazing, pressure test with dry nitrogen, evacuate and charge by weight. Protect the valve from heat while brazing as the manufacturer describes.

      ✓ Check: The valve opens and closes as it should, there is no leak at the new joints, and the work is recorded in the logbook where the refrigerant rules require it.

  2. 2
    Flowchart A

    The controls do not cut out: sensor, setpoint or thermostat.

    Remedy: Compare the sensor with a calibrated thermometer and check the setpoint and the sensor location. If the controller output is off but the coil still has voltage, a relay or contactor is stuck.

    🛠 How do I do it? Step by step

    Only qualified personnel may work on refrigeration and electrical systems. Follow the manufacturer's manual and local rules; the steps are guidance, not a replacement for training.

    Check a sensor against a reference

    A temperature or pressure sensor that reads wrong makes the controller regulate wrong: wrong superheat, wrong defrost, false alarms. Compare it with a calibrated reference before changing settings or parts.

    1. Fit the reference next to the sensor. Fasten a calibrated thermometer probe beside the temperature sensor on the same pipe or in the same air stream, with heat-conducting paste and insulation. For a pressure sensor, connect a calibrated gauge to a service port at the same point in the circuit. Wear goggles and gloves when connecting to the refrigerant circuit.

      ✓ Check: The reference reading is steady for a few minutes.

    2. Compare with the controller reading. Read the live value of the sensor in the controller display or service tool at the same time as the reference.

      ✓ Check: The difference is within the tolerance given by the sensor or controller manufacturer (for a temperature sensor typically within about 1 K).

    3. Check offsets and sensor type. In the controller parameter list, check that the sensor type (e.g. NTC, PT1000, 0–10 V, 4–20 mA), the pressure range and any calibration offset match the fitted sensor. Record the original values before changing anything.

      ✓ Check: Sensor type, range and offset in the controller match the sensor data sheet.

    4. Measure the sensor resistance. Isolate and lock off the controller, disconnect the sensor and measure its resistance with a multimeter while the reference shows the temperature at the sensor. Compare with the manufacturer's resistance table. A PT1000 reads 1000 Ω at 0 °C; an ice-water bath gives a simple 0 °C check point.

      ✓ Check: The resistance matches the table value for the reference temperature; OL or 0 Ω means a broken or shorted sensor or cable.

    5. Check the sensor location and mounting. Inspect the pipe clamp or pocket: firm metal-to-metal contact, heat-conducting paste, insulation against the surrounding air and the correct position (e.g. evaporator outlet, not in the air stream of a fan).

      ✓ Check: The sensor sits firmly at the correct point and is insulated.

    6. Reconnect and confirm. Reconnect the sensor, restore power and compare the reading with the reference once more. Replace a sensor that is out of tolerance with one of the same type.

      ✓ Check: Controller and reference agree within the tolerance.

    Check controller settings and alarm log

    Many faults that look like hardware faults are wrong settings or alarms that keep repeating. Read the alarm log and compare the settings with the manufacturer's parameter list before you change anything.

    1. Read the alarm log. Open the alarm menu with the keypad or service tool and note every recent alarm code with date and time. Look up each code in the manufacturer's manual.

      ✓ Check: You have a list of alarms with times and know what each code means.

    2. Check the clock. Check the controller's date and time. A wrong clock shifts scheduled defrosts and night setback and makes the alarm log misleading.

      ✓ Check: The controller clock shows the correct local date and time.

    3. Record all settings before changing anything. Write down, photograph or export setpoints, differentials, neutral zone, minimum run and off times, anti-short-cycle timer, defrost interval and duration, and the operating mode.

      ✓ Check: The service report holds a complete copy of the original settings.

    4. Compare with the parameter list. Compare each value with the manufacturer's parameter list and the plant documentation. Look in particular for a differential that is too small (short cycling), timers set to zero and setpoints that do not match the application.

      ✓ Check: Every deviation is noted with the original and the recommended value.

    5. Check the safety limits. Compare low and high pressure cut-outs and temperature limits in the controller with the manufacturer's values. Never set a safety limit beyond the manufacturer's values, and the high pressure cut-out must stay below the safety valve set pressure.

      ✓ Check: All safety limits are within the manufacturer's values.

    6. Change one value at a time and test. Correct one setting at a time, check the operating mode, and let the system run long enough to see the effect. Record every change in the service report.

      ✓ Check: The system runs as expected and the alarm does not return.

    Trace the control and safety chain

    When a compressor or fan does not get a start signal, follow the control voltage through the safety chain in the wiring diagram to the point where it disappears. Live measurements in an open panel are for qualified personnel only.

    1. Get the wiring diagram. Find the diagram for the unit and mark the path from the control supply through fuses, safety devices (HP/LP switches, motor protection, thermal protection) and controller outputs to the contactor coil. Use a CAT III/IV meter with insulated probes.

      ✓ Check: The diagram matches the unit's model and serial plate, and you know the order of the devices.

    2. Check the control supply. Measure the voltage at the secondary of the control transformer or power supply and check the control fuses.

      ✓ Check: The rated control voltage (e.g. 24 V AC or 230 V AC) is present and the fuses are intact.

    3. Follow the chain device by device. Measure from each terminal in the chain to neutral or control common, in the order of the diagram. Never bridge a safety switch to make the system run.

      ✓ Check: You find the point where voltage is present on the input but 0 V on the output: that device is open.

    4. Find out why the device is open. Read the device: is the HP switch tripped and does it have a manual reset, is the motor protection tripped, is a door or flow switch open? Check the cause (pressure, current, temperature) before resetting.

      ✓ Check: The cause of the trip is known, not only the device.

    5. Check the controller output and relays. With a call for operation active, measure the output at the controller relay terminal. A relay that is energised but has no voltage on its output, or that stays closed without a call, is faulty.

      ✓ Check: The output follows the call: voltage when the controller calls and none when it does not.

    6. Repair and test. Isolate and lock off before replacing a part or tightening terminals. Restore power, reset and check that the chain closes and the contactor pulls in.

      ✓ Check: The system starts on call and stops when each safety device opens.

  3. 3

    A relay or contactor is stuck, so the coil is energised all the time.

    Remedy: Measure the output with the controller in stop and replace the relay.

    🛠 How do I do it? Step by step

    Only qualified personnel may work on refrigeration and electrical systems. Follow the manufacturer's manual and local rules; the steps are guidance, not a replacement for training.

    Trace the control and safety chain

    When a compressor or fan does not get a start signal, follow the control voltage through the safety chain in the wiring diagram to the point where it disappears. Live measurements in an open panel are for qualified personnel only.

    1. Get the wiring diagram. Find the diagram for the unit and mark the path from the control supply through fuses, safety devices (HP/LP switches, motor protection, thermal protection) and controller outputs to the contactor coil. Use a CAT III/IV meter with insulated probes.

      ✓ Check: The diagram matches the unit's model and serial plate, and you know the order of the devices.

    2. Check the control supply. Measure the voltage at the secondary of the control transformer or power supply and check the control fuses.

      ✓ Check: The rated control voltage (e.g. 24 V AC or 230 V AC) is present and the fuses are intact.

    3. Follow the chain device by device. Measure from each terminal in the chain to neutral or control common, in the order of the diagram. Never bridge a safety switch to make the system run.

      ✓ Check: You find the point where voltage is present on the input but 0 V on the output: that device is open.

    4. Find out why the device is open. Read the device: is the HP switch tripped and does it have a manual reset, is the motor protection tripped, is a door or flow switch open? Check the cause (pressure, current, temperature) before resetting.

      ✓ Check: The cause of the trip is known, not only the device.

    5. Check the controller output and relays. With a call for operation active, measure the output at the controller relay terminal. A relay that is energised but has no voltage on its output, or that stays closed without a call, is faulty.

      ✓ Check: The output follows the call: voltage when the controller calls and none when it does not.

    6. Repair and test. Isolate and lock off before replacing a part or tightening terminals. Restore power, reset and check that the chain closes and the contactor pulls in.

      ✓ Check: The system starts on call and stops when each safety device opens.

  4. 4
    Flowchart C

    The room is cooled from outside: cold weather, an adjacent freezer room or cold air from another room, and there is no heating.

    Remedy: Fit heating controlled by the room thermostat (with a neutral zone), or insulate and seal against the cold space.

Checks from the manufacturers’ manuals (9)

Values and checks the manufacturers give for their own products; they apply to the product named.

  • Dixell XR460C; Full Gauge MT-512E Log: With a failed room probe (alarm P1 or Err) many controllers run the compressor on a fixed emergency timer (Dixell COn/COF, Full Gauge 15 min on/15 min off by default); with off-time set to 0 the compressor runs all the time, so the room gets too cold or too warm. Replace the probe and check these settings.[2]
  • Castel solenoid valves: A solenoid valve that will not seal is often an installation fault: fitted against the arrow on the body, mounted with the coil pointing down so dirt settles in the armature tube, or sealing tape/paste blocking the pilot holes. Pilot-operated and piston valves are especially sensitive to debris; fit a strainer upstream.[3]
  • Copeland EXD-SH1/2 with EX/CX valves: Where an electronic expansion valve also acts as the liquid shut-off, it only closes fully when its run/digital input is switched off; a permanently jumpered or wrongly wired input, or a wrong valve type/current setting, leaves it partly open at standstill.[4]
  • Heatcraft Beacon II with EEV: Test whether an electronic expansion valve really closes: put the system in pump-down/service mode. If the LP switch opens within the pump-down time the valve seals; if pump-down times out, the valve leaks or the LP switch is set too low.[5]
  • LG Multi V 5 VRF: VRF: to find an indoor unit whose expansion valve leaks when closed, run that unit in fan mode while another unit cools. If its liquid pipe temperature drops low, its EEV passes refrigerant and must be replaced.[6]
  • HTPG EcoNet unit coolers: Oversized system or low load: the controller keeps cooling for its minimum compressor run time after the set point is reached and overshoots. HTPG suggests shortening the minimum run time from 5 to 3-4 minutes or raising the superheat set point.[7]
  • Toshiba multi-split RAS-5M: Multi-split: the electronic valve of a room that is switched off leaks, so that room keeps cooling while the others run; Toshiba reports this as a valve leakage error.[8]
  • Daikin VRV, VRV-III and VRV-WII systems (RXYQ, REYQ, RWEYQ) with FXxQ indoor units: In cooling, a VRV indoor unit at thermostat-off closes its expansion valve completely (0 pulses), while in heating a stopped or thermostat-off unit keeps a minimum opening of about 200 pulses so that refrigerant does not collect in it. A room that keeps getting colder while its unit is at thermostat-off in cooling therefore points to an expansion valve that does not close; Daikin also warns that oversized indoor units give large temperature swings.[9]
  • Daikin VRV, VRV-III and VRV-WII systems (RXYQ, REYQ, RWEYQ) with FXxQ indoor units: A VRV indoor unit uses the sensor in the remote controller only when the return air is close to set point (with 75 °F set: about 73–81 °F when the temperature rises) and the return air thermistor otherwise. Where outdoor air is mixed into the return air, the return temperature can stay outside that band, so the room ends up away from set point; Daikin's remedy is a separate remote sensor (KRCS01-1) in the room.[10]
📝 Fill in a service report

Sources

  1. Danfoss Ref Tools – Troubleshooter: solenoid valve does not close or closes partially
  2. Dixell – XR460C operating manual + Full Gauge – MT-512E Log manual (Ver.09), p. 3 (COn, COF, P1) | p. 3 (F15–F17)
  3. Castel – Solenoid valves handbook VS-ED 01/2017 | Castel – GoGreen Technical Handbook 2023, Castel: p. 55 (VS-ED 01/2017) | Castel: solenoid valves – installation
  4. Copeland – EXD-SH1/2 operating instructions Rev08 (18.11.2025), service/troubleshooting table (OI EXD-SH12 Rev08, 18.11.2025)
  5. Heatcraft – Beacon II installation and operation manual H-IM-79G, p. 27, 33 (H-IM-79G)
  6. LG – Multi V 5 Outdoor Unit Service Manual (09/18), Checking the High/Low Pressure Sensors, p. 122
  7. HTPG – Troubleshooting Guide EcoNet enabled unit coolers, HTPG0425_TSG (Jan 2025), pp. 13-14
  8. Toshiba – Service manual multi-split RAS-5M34G3AVG-E, SVM-23012 (2023), pp. 118-120
  9. Daikin AC (Americas) – VRV Service & Troubleshooting, Participant Guide: VRV Systems Basic Operation Guide, Engineering Data EGVUSE09-07C (09/2007), with VRV III service manual navigation and Service Checker Type III workshop slides, 3.1 Cooling Operation, p. 4; 3.2 Heating Operation, p. 5
  10. Daikin AC (Americas) – VRV Service & Troubleshooting, Participant Guide: VRV Systems Basic Operation Guide, Engineering Data EGVUSE09-07C (09/2007), with VRV III service manual navigation and Service Checker Type III workshop slides, 4.1.1 Operation Range of Remote Controller Temperature Sensor, p. 8–9
Disclaimer: This text is guidance, not legal advice. It summarises regulations and standards and does not replace the official text. Always check the version in force and local requirements.
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