Air conditioners in Sunnyvale, Santa Clara and Cupertino work hardest from June to September, when hot spells push afternoons into the 90s and a system that idled through spring suddenly runs for hours. Most of the trouble we see then is not a dead system but one weak part, a dirty coil or an airflow restriction. So every job starts with a diagnosis: symptoms, airflow, controls, electrical readings, system age and repair history. Good advice keeps maintenance, targeted repairs and replacement timing apart instead of jumping straight to new equipment.
Before the visit: describe what changed
You save diagnostic time when you can tell the technician:
- What changed and when — after a hot day, after a power outage, or gradually over a few weeks.
- Whether the system starts — indoor fan only, outdoor unit only, both, or nothing at all.
- The main symptom — airflow, temperature, noise or water.
When you book, ask which checks the visit includes: controls, electrical readings, airflow, visible wear, safety switches and access to the equipment.
Which service fits your situation
| What is going on | Where to start |
|---|---|
| AC runs but the house stays warm, or it will not start | AC repair |
| No cooling at all during a hot spell | Emergency AC repair |
| System is old, repairs keep coming, or you want central air added | AC installation |
| Eichler, addition or rooms the ducts never reached | Ductless mini-splits |
| Office or shop with many zones on one refrigerant system | VRF/VRV systems |
Repairs
AC repair covers most no-cooling and weak-cooling calls. The parts most often behind them each have their own page:
- Capacitor replacement — a weak run capacitor is the most common reason an outdoor unit hums without starting.
- Fan motor repair — a seized or overheating condenser fan motor leaves the unit unable to shed heat.
- Compressor repair — compressor complaints are confirmed with electrical and pressure readings first, because a bad capacitor or contactor can look exactly the same.
- Refrigerant recharge — a system that is low on refrigerant has a leak, so the leak is found before any refrigerant goes in.
If the system quits in the middle of a heat spell, emergency AC repair explains what to do while you wait.
Installation and replacement
AC installation starts with a load calculation, not the size of the old unit. AC replacement swaps a failing system for one matched to the existing furnace or air handler, while central air conditioning covers adding whole-home cooling to a house that was built with a furnace and ducts but no AC.
Ductless and multi-zone cooling
Many Eichler homes have radiant heat in the concrete slab and no attic for ducts, so cooling them usually means ductless mini-splits. Mini-splits also suit room additions and converted garages. Commercial buildings with many zones on one refrigerant system are covered on the VRF/VRV systems page.
Maintenance and coil cleaning
A yearly AC tune-up in spring checks the electrical parts, the condensate drain and the refrigerant side before the first hot spell. Coil cleaning restores heat transfer on both the indoor evaporator and the outdoor condenser. A maintenance plan puts these visits on a schedule so you do not have to remember them.
Thermostats and ducts
Some “AC problems” are really controls or ductwork. Thermostat service covers wiring faults, misreading sensors and new thermostat installs. Duct repair fixes crushed or disconnected runs in attics and crawlspaces, a common reason one bedroom never cools in older single-family homes.
Parts that fit your equipment
We are independent and not affiliated with any manufacturer. Parts are chosen for your brand, model, age and warranty situation, and when a system may still be covered by its manufacturer’s parts warranty, we check before you approve the repair.
Keeping cooling costs down
- Change the filter on schedule; a clogged one cuts airflow and stretches run times.
- Keep plants and stored items a couple of feet away from the outdoor unit.
- Set the thermostat a few degrees higher when nobody is home.
- Have leaky attic ducts sealed; here is why duct sealing pays off.
- Replace a worn-out system that needs a major repair instead of nursing it along.
More ideas are in our summer energy-saving tips.
Local notes
Late summer and fall can bring wildfire smoke. Most central systems recirculate indoor air, so running the fan with a good filter helps clean the air inside on smoke days; see wildfire smoke filtration. For city-specific details, see air conditioning in Sunnyvale, Santa Clara and Cupertino.