Commercial rooftop unit service in San Jose starts with what is actually failing on the roof. A rooftop unit, or RTU, is a packaged system: compressor, condenser coil and fans, evaporator coil, blower and either a gas heat section or a heat pump, all in one cabinet on a curb above the space it serves. Sitting in full sun on a dusty roof, a few of its parts wear faster than anything else in the building. Most repairs run $200–$2,000, and you see the price before work begins.
Common RTU problems
| What you notice | Likely cause | What it usually takes |
|---|---|---|
| Unit runs but the space won’t cool on hot afternoons | Dirty condenser coil, economizer stuck open, low refrigerant | Coil cleaning, damper or actuator repair, leak search |
| Weak airflow, squealing from the cabinet | Worn or loose blower belt, clogged filters | Belt and pulley service, filter change |
| Condenser fan not turning, unit trips off | Failed fan motor or capacitor | Motor or capacitor replacement |
| No heat on a cold morning | Ignition, flame sensor, inducer or limit fault | Gas heat diagnosis and repair |
| Water in the ceiling below the unit | Clogged condensate drain or missing trap, or a failed curb seal | Drain and trap repair, or a roofer for the curb |
| High energy bills with no obvious fault | Economizer not working, dirty coils, poor schedules | Economizer test, coil cleaning, control settings |
| Unit short-cycles | Sensor placement, oversized unit, control fault | Testing before any part is changed |
Economizers
Most RTUs have an economizer: outdoor-air dampers, an actuator that moves them, sensors and a controller. When the outdoor air is cool enough, the dampers open and the space is cooled with outdoor air instead of the compressor. Economizers are often the most neglected part of a rooftop unit. A damper linkage seizes, an actuator fails or a sensor drifts, and nobody notices until the bills climb or the space overheats.
Stuck open on a hot San Jose afternoon, the unit pulls in hot outdoor air and can’t keep up. Stuck closed, it misses free cooling on cool mornings and evenings and may bring in less outdoor air than the space needs. On maintenance visits we run the economizer through its full range and check that the sensors read what the weather is actually doing.
What a San Jose roof does to an RTU
Hot, dry summers are hard on rooftop equipment. The air just above a sunny roof is hotter than the air at street level, and that is the air the condenser has to reject heat into. Dust, pollen and leaves pack the condenser coil, so the unit sheds heat less well exactly when it needs to most. On smoke days, outdoor-air filters and coils pick up soot and ash quickly, and a filter change after a smoky stretch is cheap insurance. Belts dry out and stretch, and cabinet panels and gaskets weather.
Below the roof, older buildings often have duct connections at the curb that have loosened over the years, so cooled air leaks into the ceiling space before it reaches the rooms. A unit that seems too small is sometimes losing part of its output right there.
Preventive maintenance
A rooftop maintenance visit covers:
- filters changed and the filter rack checked for gaps;
- blower belt and pulleys inspected, tensioned or replaced;
- condenser and evaporator coils inspected and cleaned as needed;
- condensate pan, drain and trap cleared;
- compressor and fan motor amp draw measured, capacitors and contactors tested;
- economizer dampers, actuator and sensors tested through their range;
- gas heat section: burners, ignition, flame sensor, inducer, heat exchanger and flue;
- cabinet panels, gaskets and the curb connection looked over.
Long operating hours, dusty work and busy roofs call for more frequent visits. For several units across a property, our commercial HVAC page covers maintenance agreements for businesses.
Repair or replace an aging unit
Repair makes sense when one part has failed on a unit that is otherwise sound. Replacement becomes the real question when an older unit needs a compressor or a heat exchanger, when it still runs on R-22 (a refrigerant no longer produced in the US, so repairs that need it get expensive), or when rust and repeat repairs keep piling up. Replacing an RTU usually means a crane lift, often a curb adapter if the new unit’s footprint differs, and a permit. Estimates for replacements are free, and you get a written estimate before anything is ordered.
What affects the price
Rooftop unit service typically runs $200–$2,000. Belts, filters, capacitors and contactors are at the low end. Fan motors, economizer actuators and controllers, ignition parts and refrigerant leak repairs sit higher. Access matters too: a unit reached by a fixed ladder and roof hatch is quicker to work on than one that needs special arrangements. Compressor and full unit replacements are quoted separately.
Refrigerant work is done by EPA-certified technicians. Urgent calls are taken 24/7, and for a unit that has quit and can’t wait, see emergency HVAC.