An air conditioner in Tiburon, Belvedere or Mill Valley can sit unused from October to June and then be asked to cool a sun-filled living room on the first warm afternoon. That is when weak parts give out. Most no-cooling calls come down to one of five things: a failed electrical part (capacitor, contactor, fuse), restricted airflow, a dirty or corroded outdoor coil, a blocked condensate drain, or a refrigerant leak. A proper repair visit tells them apart with measurements before anything is replaced.
How we diagnose an AC that isn’t cooling
- Electrical. We test the capacitor, contactor, fuses, disconnect and thermostat wiring, and measure the current the compressor and fan motors draw. These parts fail far more often than compressors do.
- Airflow. Filter, blower, return grilles and the temperature drop across the indoor coil. Low airflow can freeze the coil and look exactly like low refrigerant.
- Safety controls. High-pressure and float switches, the condensate drain and the secondary pan. A tripped float switch shuts the system off with no other sign.
- Refrigerant. Only after the first three check out do we connect gauges. A low charge means a leak somewhere, and topping up without finding it only postpones the next call. Refrigerant work is done by EPA-certified technicians.
Symptoms and what usually causes them
| What you notice | Usual cause | Typical fix |
|---|---|---|
| Outdoor unit hums, fan doesn’t turn | Failed capacitor or seized fan motor | Replace the capacitor or motor |
| Indoor fan runs, air is warm | Stuck contactor, tripped breaker, compressor not starting | Electrical testing, then the failed part |
| Ice on the copper line or indoor coil | Dirty filter, weak blower or low charge | Thaw, fix airflow, leak search if needed |
| Water near the furnace or air handler | Clogged condensate line | Clear the drain, test the float switch |
| Cool in the morning, behind by late afternoon | Dirty or salt-corroded outdoor coil | Coil cleaning, then a check of sizing for sunny rooms |
| Breaker trips at start-up | Shorted motor, compressor fault or wiring | Electrical diagnosis before any more resets |
What a repair costs
The diagnostic visit is $79–$99, and the fee is waived when you approve the repair. After the diagnosis you get an upfront price for the repair, before any work begins, with no hidden fees. What moves that price: whether the fault is electrical (capacitors and contactors are usually fixed on the first visit), whether it is in a motor or in the refrigerant circuit, which refrigerant the system uses, and access. An air handler in a tight attic or crawlspace takes longer than one in a garage. For larger repairs, flexible financing is available with approved credit.
Repair or replace?
Fix it when one part has failed and the system otherwise cools the house evenly. Replacement is worth discussing when an older system needs a compressor or an indoor coil, when it still runs on R-22 (no longer produced, so every recharge gets harder), or when the same repair keeps coming back. In a mild climate a heat pump can replace both the air conditioner and the furnace; our AC installation page walks through the options.
What you can check before calling
- The thermostat is set to Cool, a few degrees below room temperature, with fresh batteries.
- The filter is not grey and clogged.
- The breakers are on and the outdoor disconnect is in place.
- Leaves, plants and stored items are clear of the outdoor unit.
- If you see ice, switch cooling off and run the fan only until it melts.
If the outdoor unit hums without the fan turning, or the breaker trips again, leave the system off. Repeated starts can damage the compressor.
AC repair in Tiburon, Belvedere and Mill Valley
On the peninsula, salt air corrodes coil fins, electrical terminals and cabinet screws faster than it does inland, so outdoor units near the water fail at their connections and coils sooner. Many larger homes have more than one zone, and a single zone that stops cooling is often a damper or thermostat fault rather than the equipment. In Mill Valley, older homes often have ducts and condensate lines in the crawlspace, where clogged drains and crushed returns are common. The local pages cover AC repair in Tiburon, Belvedere and Mill Valley, and a spring AC tune-up catches weak parts before the first warm spell.