AC suddenly won't run at all — check the condensate float switch (any brand)

What this error means

If the thermostat is calling for cooling but the system is completely dead, there's a decent chance nothing is broken: the condensate drain clogged, water backed up, and the float safety switch cut the system off before the pan overflowed into your ceiling. It's protecting you. The fix is clearing the drain, and it's a 15-minute job.

Symptoms

• AC completely unresponsive though the thermostat calls for cooling
• Water visible in the drain pan under the indoor unit/air handler
• Water stains appearing on the ceiling below the unit (act now)

Try this first (safe DIY steps)

1. Kill power to the system
2. Find the condensate drain line's exterior termination (a PVC pipe outside, usually near the outdoor unit or an exterior wall)
3. Attach a wet/dry shop vac to it, seal with a rag, and run it 1–2 minutes — you'll usually hear the clog pull through
4. Empty the drain pan, restore power
5. Prevention: a cup of distilled vinegar down the drain line's access tee every few months

Safety: power off before any physical intervention. Never bypass covers or interlocks — fuser areas run hot enough to burn.

When to call a technician

If the vac doesn't clear it, or there's no float switch and water is already spreading: drain clearing service runs $75–$200 — cheap against ceiling repairs.