AC Dead and Will Not Start in Oakland

Rule these out first

1. Thermostat screen on, batteries fresh, mode set to Cool.
2. Breakers for the condenser and the furnace or air handler switched on. Reset a tripped one once.
3. Service switch near the furnace turned on. It looks like an ordinary light switch.
4. Furnace or air handler door closed tight. A safety switch behind it keeps the blower off when the panel is loose.
5. Condensate pan dry. A float switch shuts the system down when the pan fills.

Parts that often fail

When those check out, the usual suspects are a blown low-voltage fuse on the furnace control board, a failed transformer, a bad contactor or a broken thermostat wire. Power flickers and outages can damage boards and contactors too.

A breaker that trips a second time points to a short or a compressor pulling too much current. Leave it off and call.

Questions about AC Will Not Start in Oakland

The outdoor unit runs but nothing comes out of the vents. What now?

The indoor blower is not running. Shut the system off so the coil does not freeze, and have the blower motor, its capacitor and the board checked.

Can a clogged drain really stop the whole system?

Yes. A float switch in the pan or drain line cuts the cooling when water backs up, which protects the ceiling and floor below.

Should I replace the thermostat myself?

If you are comfortable with low-voltage wiring and label each wire, it is a reasonable job to do yourself. Heat pumps and multi-stage systems are easier to get wrong.