Trane AC Not Cooling: Causes, Fixes & Repair Costs
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Trane air conditioner not cooling: what it means
“Not cooling” is a symptom, not a stored fault code. Your Trane air conditioner may be running with warm or barely cool air coming from the vents. Or the indoor blower may run while the outdoor unit stays silent. Either way, the system isn’t removing heat from your home.
Most Trane single-stage units (many XR and XL models) have no diagnostic display. The cause has to be found by inspection and testing. Two-stage and variable-speed models (XV series and ComfortLink II communicating systems) may log alerts on the thermostat or outdoor board. Those alerts include low-pressure, high-pressure, and compressor protection trips.
Reset behavior depends on the model:
- Pressure-switch and internal compressor overload trips usually reset automatically after a cool-down or time delay.
- Some communicating systems lock out after repeated trips. They then need a power cycle or a technician reset.
If you have a Trane heat pump rather than a straight AC, see Trane Heat Pump Not Cooling instead.
Trane air conditioner not cooling: common causes, ranked by probability
- Dirty or clogged air filter. Restricted airflow reduces cooling and can freeze the indoor coil.
- Thermostat setting or power issue. Common examples are the wrong mode, fan set to On instead of Auto, dead batteries, or a setpoint that’s too high.
- Failed run capacitor. This is the most common electrical failure in outdoor units. The compressor or fan hums or won’t start.
- Bad contactor or tripped breaker/disconnect. The outdoor unit gets no power or no control signal.
- Dirty outdoor condenser coil. Debris, cottonwood, or grass clippings block heat rejection, which raises pressures and can trip the high-pressure switch.
- Low refrigerant from a leak. This causes a frozen evaporator coil, ice on the suction line, and weak cooling. Leaks are common on older evaporator coils.
- Frozen evaporator coil. It is usually a result of cause 1 or 6, or of a weak blower.
- Outdoor fan motor failure. The compressor overheats and cycles off on internal overload.
- Clogged condensate drain tripping a float switch. On many installs this cuts the thermostat signal and shuts cooling off.
- Compressor failure. This is the least likely cause and the most expensive one.
How to fix Trane air conditioner not cooling: safe checks first
- Thermostat: Confirm it is set to Cool, the setpoint is below room temperature, and the fan is on Auto. Replace the batteries if the display is blank or dim.
- Air filter: Replace it if it’s gray or clogged. Never run the system without a filter.
- Breakers and switches: Check the indoor furnace/air handler breaker and switch. Check the outdoor AC breaker too. If a breaker is tripped, reset it once. If it trips again, stop and call a technician.
- Frozen coil: If you see ice on the copper line at the outdoor unit or at the indoor coil, set the system to Off with the fan On until the ice melts. Don’t chip at the ice.
- Vents and returns: Open the supply registers and clear furniture or rugs away from the return grilles.
- Outdoor unit surroundings: Clear leaves and debris and keep about 2 feet of clearance around it. Gently hosing the outside of the fins with the power off at the disconnect is fine. Don’t remove panels.
- Condensate line: If the drain pan is full or a float switch has tripped, clear the line opening with a wet/dry vac. Cooling may then resume.
- Panels: Make sure the indoor blower door is fully seated, since some units won’t run without it.
How a technician will diagnose it
- Confirms 24V call for cooling at the outdoor unit and checks the thermostat wiring.
- Checks line voltage and the contactor, looking for pitted contacts or a failed coil.
- Tests the run capacitor in microfarads against its rating.
- Measures compressor and fan motor amps and checks the windings for open, shorted, or grounded readings.
- Connects gauges and checks superheat and subcooling against the Trane charging chart. Many Trane units use a TXV and are charged by subcooling.
- Measures temperature split across the indoor coil (typically 16–22°F) and static pressure for airflow.
- Leak-searches with an electronic detector, bubbles, or nitrogen if the charge is low.
- On XV and communicating models, reads stored alerts on the thermostat or control board.
Red flag in a quote: “just add refrigerant” with no leak search, especially if it’s a repeat top-off.
Symptom, cause and what to do
| Symptom | Likely cause | DIY action | Technician job |
|---|---|---|---|
| Weak airflow, warm air | Dirty filter | Replace filter | Check blower and static pressure |
| Indoor fan runs, outdoor unit silent | Capacitor, contactor, breaker | Check/reset breaker once | Test and replace capacitor or contactor |
| Outdoor unit hums, doesn’t start | Failed capacitor or stuck compressor | Turn off at thermostat | Replace capacitor, add hard-start kit, test compressor |
| Ice on lines or coil | Low refrigerant or airflow | Off + fan On, replace filter | Leak search, repair, recharge |
| Outdoor fan not spinning | Fan motor or capacitor | None | Replace motor or capacitor |
| Runs constantly, air only slightly cool | Dirty condenser, low charge | Clear debris, rinse fins | Coil cleaning, charge check |
| AC stops, water in drain pan | Condensate float switch tripped | Clear the drain line | Clean drain, replace pump or switch |
| Breaker trips repeatedly | Shorted compressor or motor | Don’t keep resetting | Electrical diagnosis |
Trane air conditioner not cooling repair cost
These are typical US ranges, including labor.
| Repair | Typical cost |
|---|---|
| Diagnostic / service call | $80–$200 |
| Run capacitor replacement | $120–$350 |
| Contactor replacement | $150–$350 |
| Hard-start kit | $200–$400 |
| Outdoor fan motor | $350–$800 |
| Condenser coil cleaning | $100–$250 |
| Condensate drain clearing / float switch | $100–$250 |
| Leak search | $150–$500 |
| Refrigerant recharge (R-410A, per job) | $200–$700 |
| Evaporator coil replacement | $1,200–$3,000 |
| Compressor replacement | $1,800–$3,500+ |
R-22 systems cost far more to recharge, and the refrigerant is often not worth adding. Coils and compressors may be covered under Trane’s registered-unit parts warranty, typically 10 years for the compressor. Labor usually isn’t covered.
Related codes
- Trane Heat Pump Not Cooling
- Trane Heat Pump Compressor Not Running
- Trane Heat Pump Outdoor Fan Not Spinning
- Trane Heat Pump Breaker Keeps Tripping
- Trane Heat Pump Runs Constantly
- Trane Heat Pump Short Cycling
- Trane Furnace Blower Not Running
- Trane Furnace Leaking Water
Parts & tools for this fix
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Frequently asked questions
Why is my Trane AC running but not cooling the house?
The most common reasons are a clogged air filter, a dirty outdoor coil, or an outdoor unit that isn't running. The outdoor unit can stop because of a failed capacitor or contactor. Low refrigerant from a leak is also common. If the indoor fan runs but the outdoor unit is silent, call a technician.
Can I add refrigerant to my Trane AC myself?
No. Handling refrigerant requires EPA Section 608 certification. If your system is low, it has a leak. A technician should find and repair the leak, not just top it off.
My Trane AC coil is frozen. What should I do?
Set the thermostat to Off and the fan to On so the ice melts, which can take several hours. Check and replace the filter and make sure supply vents are open. If it freezes again, the likely cause is low refrigerant or an airflow problem that needs a technician.
Is it worth repairing an older Trane AC that isn't cooling?
Capacitor, contactor, and fan motor repairs are usually worth doing at any age. If the compressor fails or a coil leaks on a unit over 12–15 years old, especially an R-22 system, replacement often makes more financial sense.