In shortYOİ Mühendislik diagnoses spare parts with measurements for all-brand air conditioners, VRF, chillers, fan coils, air handling units, rooftop units and precision air conditioners, supplies them as original or suitable equivalent options, and installs them. On this page you can find the functions of the most frequently replaced parts, their approximate check and replacement intervals, fault symptoms and solutions.
How we workAll unitsSplit and VRFChillerAir handling unit, fan coil, rooftopPrecision air conditioningOriginal or equivalentFAQ
Our spare parts service
Most faults in an HVAC unit start from a single part that has reached the end of its life: a dried-out capacitor, a burnt contactor, a drifting sensor or a clogged filter. Finding the right part is as important as replacing it with the right diagnosis; a part replaced on a wrong diagnosis wastes both money and time.
At YOİ Mühendislik, for air conditioners, VRF, chillers, fan coils, air handling units, rooftop units and precision air conditioners of all brands, we diagnose spare parts with measurements, supply them and install them. We don't just sell the part; we install and commission it and report the measured values.
- Diagnosis: We confirm the fault with measurements (current, pressure, temperature, resistance, capacitance, megger). We replace parts based on measurements, not guesses.
- Part identification: We work out the part code from the unit label, model and serial number; on older units, we measure the part's technical values.
- Quote: We present original and suitable equivalent options in writing, together with the lead time. The decision is yours.
- Installation and commissioning: We install the part, run the system and record the measured values.
- Record: We enter the replaced part and its date into your equipment inventory, so you can anticipate the next replacement time.
Important: The replacement and check intervals below are approximate values based on general field experience. Actual life varies significantly with the unit's brand, operating hours, environmental conditions (dust, humidity, salty air), power grid quality and maintenance routine. The final decision should always be made by measurement.
Spare parts common to all units
| Part | Function | Check / replacement | Fault symptom | Solution |
|---|---|---|---|---|
| Air filter | Removes dust from the air going to the indoor unit and coil. | Cleaning every 1–3 months on splits and fan coils; replacement on air handling units based on differential pressure. | Low airflow, icing, bad odor, high electricity consumption. | Cleaning or replacement. See our HVAC filters page for details. |
| Filter drier (dehydrator) | Traps moisture and particles in the refrigerant circuit. | Renewed every time the refrigerant circuit is opened and when the compressor is replaced. | Temperature difference between drier inlet and outlet, sweating or icing, low suction pressure. | Drier replacement, vacuum and refrigerant charging. If there is acid, system cleaning. |
| Contactor | Powers the compressor and fan motors. | Contact surface and coil checked at every maintenance; replaced if burning is seen. | Compressor does not start, humming sound, blackened or welded contacts. | Contactor replacement; the cause of the overcurrent is also investigated. |
| Capacitor | Provides starting and running torque to single-phase compressor and fan motors. | Microfarad measurement during maintenance; replaced if the value has dropped or the capacitor is swollen. | Fan or compressor does not start, turns slowly, trips thermal protection; swelling on the capacitor. | Replacement with a capacitor of the same µF and voltage rating. |
| Temperature sensor (NTC/thermistor) | Lets the board read room, pipe and discharge temperatures. | Resistance measurement when there is a fault code or drift. | Sensor fault code, unnecessary shutdowns, wrong mode changeovers. | Measurement against the resistance-temperature table; replacement if necessary. |
| Pressure switch (HP/LP) | Protects the system at excessively high or low pressure. | Set value and contact test once a year. | Frequent high/low pressure faults, unit does not start. | First the root cause raising or lowering the pressure is fixed, then the pressure switch is tested or replaced. |
| Electronic board | Manages the unit's operating logic and protections. | Check after a fault code, humidity or overvoltage. | Dark display, communication error, relay not pulling in, burn marks on the board. | Board repair or replacement; mains protection (voltage protection relay) is recommended. |
| Remote control and thermostat | Transmits the user's set value and mode selection. | In case of a fault. | Unit does not accept commands, display error, wrong temperature reading. | Battery, cable and communication check; replacement with a compatible controller. |
| Copper pipe, flare fittings and insulation | Carries the refrigerant and prevents condensation and energy loss. | Visual check at every maintenance; insulation exposed to UV and outdoor conditions can wear out in 5–10 years. | Oil traces (leak), sweating, dripping, disintegrated insulation. | Leak detection, weld repair, insulation renewal. |
Split, cassette, ducted and VRF air conditioner parts
| Part | Function | Check / replacement | Fault symptom | Solution |
|---|---|---|---|---|
| Compressor (rotary, scroll, inverter) | Runs the cycle by compressing the refrigerant. | Life varies with usage; current and pressures are checked at every maintenance. | High current, noisy operation, failure to start, thermal trip, no cooling. | Winding (megger) and current measurement; replacement if appropriate, cleaning if there is acid. |
| Indoor and outdoor fan motor | Moves air across the coils. | Bearing noise and speed are checked at every maintenance. | Noise, vibration, low speed, fan not turning. | Motor or bearing replacement; fan blade balancing. |
| Electronic expansion valve (EEV) and coil | Regulates the amount of refrigerant going to the evaporator. | Checked when superheat values drift. | Low or high superheat, icing, loss of efficiency, valve fault code. | Coil resistance and valve movement test; coil or body replacement. |
| 4-way valve | Reverses the cycle between cooling and heating. | Checked during mode changeovers. | Does not switch to heating or gets stuck in heating. | Coil test; valve replacement, vacuum and charging in case of mechanical failure. |
| Drain pump and float switch | Drains condensate water (cassette and ducted types). | Operation test and tray cleaning at every maintenance. | Water dripping, water overflow fault code. | Cleaning of the tray and line, pump or float switch replacement. |
| Louver motor (stepper motor) | Adjusts the airflow direction. | In case of a fault. | Louver does not move, noisy movement. | Motor replacement. |
| Inverter board and power module | Drives the compressor at variable speed. | After a fault code and voltage fluctuations. | Compressor drive fault code, unit runs briefly and stops. | Board and module test; repair or replacement. |
| VRF communication cable and addressing | Carries data between the indoor units and the outdoor unit. | After new installation and modifications. | Communication error, unit not detected. | Cable, polarity and address check. |
Chiller spare parts
| Part | Function | Check / replacement | Fault symptom | Solution |
|---|---|---|---|---|
| Screw and scroll compressor | Produces the chiller's cooling capacity. | Current, pressure and oil level at every maintenance; annual oil analysis is recommended for screw compressors. | High current, vibration, oil pressure fault, noisy operation. | Overhaul or replacement based on measurements and oil analysis. See our compressor overhaul page. |
| Compressor oil and oil filter | Provides lubrication, sealing and cooling. | Replacement based on oil analysis and operating hours. | Thickening, acidity, low oil pressure. | Oil and oil filter replacement; drier replacement if there is acid. |
| Crankcase heater | Prevents refrigerant from mixing into the oil during standstill. | Resistance and current measurement at the start of the season. | Foaming on cold start, oil loss, compressor damage. | Heater replacement. |
| Flow switch | Protects the compressor if there is no water flow. | Tested once a year. | Flow alarm while water is flowing, or operation with no flow. | Setting and contact check, replacement. |
| Water pump and mechanical seal | Circulates chilled water through the system. | Seal leakage and bearing noise at every maintenance. | Dripping, noise, drop in flow rate. | Seal or bearing renewal, pump overhaul. |
| Condenser fan motor | Rejects condenser heat on air-cooled chillers. | Current and bearing check at every maintenance. | High pressure fault, noise, fan not turning. | Motor or fan replacement; EC fan conversion can be considered. |
| Expansion valve (TXV/EEV) | Regulates evaporator feed. | Checked with superheat values. | Low suction, freeze protection, loss of efficiency. | Adjustment, driver or valve replacement. |
| Control board and display | Manages the chiller and logs alarms. | Alarm history is read at every maintenance. | Display error, loss of communication, relays not pulling in. | Board repair or replacement, parameter backup. |
Air handling unit, fan coil and rooftop parts
| Part | Function | Check / replacement | Fault symptom | Solution |
|---|---|---|---|---|
| Fan belt and pulley | Transmits motor power to the fan. | Tension check every 3–6 months; replacement if cracked or worn. | Squealing, belt dust, drop in airflow. | Belt replacement, pulley alignment and tension adjustment. |
| Fan and motor bearings | Lets the shaft turn without friction. | Noise and vibration at every maintenance; lubrication on greasable types. | Rumble, vibration, overheating. | Bearing replacement, balancing. |
| Fan coil motor and capacitor | Turns the fan coil fan. | Speed and current check at every maintenance. | Fan not turning, stuck at one speed, noise. | Capacitor or motor replacement. |
| Fan coil valve and actuator | Opens and closes the water going to the coil. | Open-close test at the start of the season. | Room does not heat or cool, valve constantly open. | Actuator or valve body replacement. |
| Damper motor | Adjusts the fresh air and exhaust ratio. | Movement test once a year. | Damper does not open, insufficient fresh air. | Motor replacement, linkage adjustment. |
| Coil | Heats or cools the air. | Chemical cleaning once a year. | Loss of efficiency, leaks, freeze damage. | Cleaning, leak repair or coil replacement. |
| Rooftop burner and ignition parts | Provides heating in gas-fired rooftop units. | Checked before the heating season. | No ignition, flame goes out. | Check of ignition electrode, ionization and gas valve. |
Precision air conditioning (close control) parts
| Part | Function | Check / replacement | Fault symptom | Solution |
|---|---|---|---|---|
| Humidifier cylinder | Keeps humidity within a narrow range by supplying steam to the room. | Generally replaced every 6–12 months depending on water hardness. | Low humidity alarm, cylinder full alarm, high current. | Cylinder replacement, cleaning of supply and drain lines. |
| EC fan | Provides airflow at variable speed. | Speed and alarm check at every maintenance. | Fan alarm, drop in airflow. | Fan module replacement. |
| Temperature and humidity sensor | Reports room conditions to the control board. | Compared against a reference instrument once a year. | Unnecessary humidification or dehumidification, oscillation. | Calibration or sensor replacement. |
| Water leak sensor | Detects water leaks under the floor. | Tested at every maintenance. | False alarm or no alarm. | Sensor cleaning or replacement. |
| Filter (G4/F7) | Protects electronic equipment from dust. | Based on differential pressure, generally 3–6 months. | High temperature and filter alarm. | Filter replacement. |
Original part or equivalent part?
There is no single right answer for every case. For electronic boards, inverter modules and brand-specific control parts, the original part is often the only safe option. For standard parts such as capacitors, contactors, belts, bearings, filters and filter driers, good-quality equivalents that match the technical values exactly can be used safely.
- Electronic board and inverter module: generally original
- Compressor: original or approved equivalent of the same capacity and type
- Capacitor, contactor, relay: equivalent that matches the values
- Belt, bearing, filter, filter drier: equivalent with standard dimensions
- Sensors: equivalent that matches the resistance table, or original
- Old and discontinued units: research and adaptation
In every quote we state in writing which part we recommend, why, and the lead time; the part is always chosen with your approval.
To extend the life of the part
- Have filters cleaned or replaced regularly
- Protect boards with a voltage protection relay
- Keep the outdoor unit and condenser clean
- Fix the cause of short cycling
- Have belt tension and bearings checked regularly
- Tie parts to a schedule with an annual maintenance contract
Our headquarters is in Etimesgut, Ankara. We work with a daily field team in Ankara and with a planned team from Ankara in other provinces, on a project, annual maintenance contract and public tender basis. See the areas we serve.
Frequently asked questions
Which brands' spare parts do you supply?
We supply parts for and install them on air conditioners, VRF, chillers, fan coils, air handling units, rooftop units and precision air conditioners of all brands. Sending us a photo of the unit's label speeds up part identification.
Do you only sell parts, or do you also install them?
Our priority is to take on diagnosis, parts and installation together. A part replaced on a wrong diagnosis does not fix the problem; that is why we verify the part with measurements, then install and commission it.
How do I find the part code?
The model and serial number are on the label on the unit. With this information, and a photo of the old part if needed, we work out the part code for you.
How long does part supply take?
It varies by part and brand. Standard parts arrive quickly; brand-specific or imported parts take longer. We state the lead time in writing in the quote.
My unit is discontinued; can parts still be found?
In most cases a compatible equivalent or an adaptable solution can be found. If none can be found, we report the repair and renewal options along with their costs.
Do you give a warranty on the parts you install?
We state the parts and labor warranty terms in writing in the quote, according to the type of part and its supplier.