AC Not Cooling in Los Altos

AC Not Cooling in Los Altos

Most of the time an AC that runs but will not cool is still alive, and one part has quit. Often it is a failed capacitor. Sometimes a low refrigerant charge from a slow leak, a dirty condenser coil that cannot reject heat, or a frozen evaporator coil starved of airflow. The compressor and blower are usually the last things to fail, and they are the parts people assume are dead first. We read the actual refrigerant pressures and temperatures before we name a cause, so you are not paying to replace a healthy compressor when a capacitor is the real fault.

Los Altos adds a wrinkle most cities do not. A lot of these are large ranch homes on big lots, often with a second-story pop-up or an addition that was built years after the original system went in. We see a lot of calls where the AC works fine but one wing or the added bedrooms never get there. That is not a broken AC. That is a system sized for a smaller footprint trying to cool a bigger one, and the fix is a duct and load conversation, not a part swap.

Summers here run mild with marine influence off the Peninsula, so a Los Altos AC rarely runs flat-out the way an inland system does. When it cannot keep up on a warm afternoon, that is a real signal something has changed. We find the one thing and put it on a written estimate before we touch anything.

Common causes

Failed run capacitor. This is the single most common no-cool call we get. The capacitor is what kicks the compressor and condenser fan into motion, and California heat ages them faster than the spec sheet says. We test it with a meter, and if it reads low we carry the replacement on the truck. Typical repair runs $150 to $250 and the system is cooling again the same visit.

Low refrigerant from a leak. If the charge is low, the coil cannot pull heat out of the air and the house drifts warm. Refrigerant does not get used up, so low charge means a leak somewhere. We find it with electronic detection or dye rather than just topping off and leaving. On older R-22 systems a real leak usually means replacement is the smarter spend, and we will say so plainly at the estimate.

Dirty condenser coil. On these large lots the outdoor unit often sits in landscaping that throws dust, grass clippings, and pollen into the coil fins. A clogged coil cannot reject heat, so the system runs and runs without cooling. We check the coil first because it is cheap to rule out. A proper coil cleaning often restores capacity without any parts at all.

Frozen evaporator coil from weak airflow. A clogged filter or undersized return chokes airflow across the indoor coil, it freezes into a block of ice, and warm air comes out the vents. We thaw it, find the airflow restriction, and fix the cause. On the addition-heavy homes here the real cause is sometimes ductwork that was never resized when the footprint grew.

Worn contactor. The contactor is the electrical switch that tells the outdoor unit to start. The contacts pit and burn over time, especially past eight years, and a bad one means the condenser never kicks on while the indoor blower keeps running warm air. We test it and replace it from truck stock when needed.

Undersized or unbalanced system for the current footprint. Several no-cool calls here are not a failure at all. The AC works, but it was never sized for the second story or the added wing. We re-run the load on the current floor plan and lay out the options, balancing the existing system, upsizing, or adding a dedicated ductless head for the rooms that never cool.

How we diagnose it

• Refrigerant pressures and superheat/subcooling with Fieldpiece gauges, so charge is measured, not guessed.
• Capacitor and contactor tested with a meter before any part is named on the estimate.
• Condenser and evaporator coils inspected for dirt, and the filter and return airflow checked for restriction.
• Supply temperature split across the vents in each wing, which tells us whether this is a failed part or a sizing problem on a grown footprint.
• Whether the original equipment matches the current square footage, since additions and pop-ups here often outrun the system that was installed.

$75 diagnostic, credited toward any repair over $200. You get a written quote before any work begins.

AC Not Cooling in Los Altos: common questions

Nearby and related

AC Not Cooling near Los Altos: Palo Alto · Mountain View · Cupertino .

This is usually a ac repair in Los Altos job. See our ac repair overview or the Los Altos service area.