“It runs but it is not cold,” and “it will not come on at all” are the two most common warm-weather calls we field, and both are routinely misdiagnosed as low refrigerant or a dead compressor. They rarely are. This page is the Trane-specific companion to our general AC repair service and our Trane AC repair page. Common failure modes have dedicated guides: compressor replacement, refrigerant leak, fan not spinning, leaking water, contactor replacement, and making noise.
Why a Trane runs but will not cool
From thousands of no-cool calls across SoCal, the causes cluster like this:
- Dirty condenser coil — the most common cause in a heat wave. The outdoor coil cannot reject heat, so the system loses ground as the day gets hotter. A coil cleaning plus a capacitor solves more no-cool calls in Pasadena and the Inland Empire than any other repair, often under $400 total.
- Refrigerant undercharge from a leak — not consumed, so low charge means a leak. Detection $245–$485; the fix depends on where it is.
- Weak compressor — high amp draw, cannot pull pressures down. Confirmed with gauges before we ever quote one.
- Frozen evaporator coil — ice from restricted airflow or low charge. Shut it off, thaw it, fix the restriction.
- Failed run capacitor — the unit is barely starting or the fan is struggling. Full detail on our Trane capacitor replacement page.
The full diagnostic walkthroughs are in our AC running but not cooling, why is my AC not blowing cold air, and frozen evaporator coil guides.
Why a Trane will not turn on
A no-start is usually cheaper than people fear. The common causes: a tripped breaker, dead thermostat batteries, a failed low-voltage transformer, a blown 24V control-board fuse, or a contactor welded open. If the outdoor unit hums but the fan will not spin, that is a failed run capacitor — shut the breaker so you do not cook the compressor. On a communicating XV20i paired with an XL1050, a dark or frozen thermostat screen can be a four-wire bus fault rather than a dead system, and the ComfortLink II control will usually log a 91-series communication code. The step-by-step is in our AC not turning on guide.
Why we will not just add a pound and see
Topping off a leaking Trane is a $200 bill that lasts six weeks, and it is illegal to add refrigerant without EPA certification. More importantly, it leaves the actual problem in place. We find the leak with electronic detection and a gauge set, then quote the real repair. Newer Trane systems use R-454B (the 2025-and-later refrigerant); systems through 2024 are R-410A, and a pre-2010 unit is R-22 at $150–$300 per pound — on which a leak repair rarely beats replacement. A clogged condensate drain is its own common no-cool culprit, covered in our clogged AC drain line guide.
Why it fails when it does in SoCal
The microclimate sets the pattern. Inland in Pasadena, Burbank, the Inland Empire, and the Conejo Valley, a marginal system that cools fine at 80°F loses the fight at 104°F — dirty coils and weak capacitors show worst under peak load, which is exactly when you notice. On the coast in Santa Monica, Manhattan Beach, and Malibu, salt air corrodes condenser electricals, though Trane’s Spine Fin all-aluminum coil holds up better than standard copper-aluminum. Either way, an annual coil cleaning before summer is the cheapest insurance against a peak-heat no-cool call.
Trane no-cool repair pricing
Flat-rate, parts and labor, from our SoCal service tickets. Diagnostic is $89 ($149 after-hours), credited to the repair if you proceed:
| Trane AC repair | Typical cost |
|---|---|
| Diagnostic (waived with repair) | $89 / $149 after-hours |
| Dual-run capacitor | $185–$295 |
| Contactor | $165–$285 |
| Refrigerant leak detection | $245–$485 |
| Condenser fan motor | $485–$795 |
| TXV (XR / XL systems) | $585–$895 |
| Compressor (out of warranty — we quote replacement) | $2,400–$4,200 |
These are the same flat rates on our Trane AC repair page. A registered Trane still carries labor on warranty parts; we confirm coverage before ordering.
Repair or replace
A no-cool call on a newer Trane is almost always a straightforward repair — clean the coil, replace a capacitor, fix a leak. The replace conversation starts when the cause is a failed compressor or a coil leak on an older unit: a $2,400–$4,200 compressor on a 14-plus-year R-22 system is throwing money at a degraded, end-of-life condenser. We model the repair against a written replacement quote so you decide on real numbers. See AC installation when replacement is the call, and the full lineup on our Trane brand page.