Google Nest Thermostat Not Cooling (But Heating Works)
When a Nest shows 'cooling delayed' or simply never calls for AC, the thermostat is almost always the messenger, not the problem. The real cause is usually a system-mode setting, the 5-minute compressor delay, or a wiring/power issue at the thermostat itself.
Common Causes
- The Nest is set to 'Heating' or 'Heat-Cool' mode instead of 'Cool', so it never calls for cooling
- The target temperature is set at or above the current room temperature
- 'Cooling delayed' — the built-in 5-minute compressor protection is counting down after the AC last ran
- The AC compressor is fine but the thermostat lost its C-wire power and is running on battery alone
- The cooling wire (usually Y1) isn't seated in the correct Nest base terminal, or the system type is misconfigured
- A dirty air filter or frozen evaporator coil tripped the system's safety, so it won't run at all
Step-by-Step Fix
- 1
Set the Nest to 'Cool' mode with a target below room temperature
Open the Nest app or twist the ring to the 'Cool' mode. Set the temperature at least 2-3 degrees below the current room temperature. If the AC still doesn't kick on, move to the next step.
- 2
Wait out the 'Cooling Delayed' message
Nest intentionally waits 5 minutes after the AC last ran to protect the compressor from short-cycling. If the screen says 'Cooling Delayed,' count down the full 5 minutes before deciding something is wrong.
- 3
Confirm the Nest has real power (check for the C-wire)
A Nest running only on battery can power its screen but silently fail to pull the AC contactor. In the Settings > Technical Info screen, check that the battery shows a healthy voltage. If the C-wire terminal is empty, the Nest may be under-powered — a common fix is connecting the common wire or adding the included power connector.
- 4
Verify the Y1 (cooling) wire is seated and the system type is right
Pull the Nest faceplate off and confirm the wire in the Y1 terminal (your cooling wire) is firmly seated — not stuck in the Y2 or W1 slots. Also check Settings > Equipment to make sure the Nest knows it controls cooling, not just heating.
- 5
Check the air filter and evaporator coil
A severely clogged filter or a frozen coil will trip the AC's own safety controls, which the Nest can't override. Replace the filter and, if you see ice on the indoor coil, turn the system off entirely to let it thaw before retrying.
- 6
Test the AC directly to isolate the thermostat
At the thermostat base, briefly short the R and Y wires together with the system power off, then turn power back on. If the compressor runs, the problem is the Nest; if it still doesn't, the issue is downstream in the HVAC system and you need a technician.
Still stuck?
If none of these steps fixed it, describe your exact situation to our AI troubleshooting assistant for a more specific answer.
Ask the AI AssistantFrequently Asked Questions
Why does my Nest say 'Cooling Delayed'?
It's a built-in 5-minute countdown that protects your AC compressor from short-cycling. The Nest won't call for cooling during that window, even though the screen responds instantly.
Does the Nest thermostat need a C-wire to run the AC?
For most homes, yes. Without a C-wire the Nest can run on battery for a while, but it may not have enough power to reliably trigger the cooling contactor. The included power connector or adding a common wire fixes this.
Nest says 'Cooling' but no cold air comes out. What now?
That means the thermostat is sending the signal, so the issue is downstream — usually a clogged filter, frozen coil, capacitor failure, or the outdoor unit's breaker tripping. Time to call an HVAC pro.
Why does my Nest cool sometimes but not other days?
Intermittent cooling often points to a borderline power issue (weak C-wire connection) or a failing capacitor that works when cool and struggles in peak heat. Check the technical info battery voltage first.