No air from vents

Air handler not blowing air

If the air handler is not blowing air, start with thermostat Fan On, power, filter condition, pan water, and whether any register has airflow. A no-air symptom is not enough evidence to buy blower or board parts.

Use the Fan On result. No airflow during Fan On sends you to power, safety, blower, or control checks; pan water or a raised float switch makes condensate the first visible clue.

No air from the vents can come from a command problem, safety shutdown, airflow blockage, or service-only blower fault.

Don’t start with: Do not buy blower motors, boards, relays, or hidden electrical parts from a no-air symptom alone.

No airflow from every register?Try thermostat Fan On once and check the indoor unit for power and pan water.

Filter is dirty, wet, collapsed, or wrong?Install the exact filter and retest before deeper diagnosis.

Do this first

Set the thermostat to Fan On once and listen for the indoor blower.
Check the air-handler breaker only once; do not keep resetting it.
Replace a dirty, damp, collapsed, or wrong-size filter.
Look for pan water, a raised float switch, or ice on the coil area.
Replace thermostat batteries only if your thermostat uses them and the display is weak or blank.
Call service for no Fan On response, hot smell, sharp buzzing, or repeated breaker trips.

Last reviewed: 2026-06-28

Fast symptom sorter

Fan On makes air move?

The blower can run; check the normal heat or cooling call next.

Fan On does nothing?

Check power, filter, pan water, and stop before blower controls.

Thermostat display blank?

Check batteries only if the model uses them.

Pan water or raised float?

Clear the drain clue before replacing the switch.

Breaker trips again?

Keep the system off and call service.

Prove whether the blower can move air

A controlled Fan On test plus filter, water, and register checks separates no command from no airflow.

Air handler cabinet checked when not blowing air — Start at the thermostat command, cabinet, filter slot, and drain area before assuming blower failure.

Air handler filter and drain checked when not blowing air — A blocked filter or wet pan can stop operation without proving the blower motor failed.

Supply register checked when air handler is not blowing air — Checking a register confirms whether the problem is no airflow everywhere or weak airflow at one room.

Before you buy air-handler parts

Buy only after the no-air clue is narrowed down. A filter is reasonable when it is dirty, damp, collapsed, missing, or the wrong size. A float switch is reasonable only after the pan and drain are dry and the visible switch still sticks. Match the exact filter size, switch mounting style, thermostat battery type, and confirmed diagnosis before ordering anything.

Jump to: System Split Table · Tools You May Need · Replacement Parts

What this symptom means

Start with one controlled Fan On command.

If Fan On works, the blower is capable of moving air.
If Fan On does nothing, power, safety, blower, or control diagnosis is still possible.
Pan water can interrupt operation on some systems.
A blank thermostat may be a battery problem only if that thermostat uses replaceable batteries.

What not to do first

Avoid buying internal parts until the visible clues support it.

Do not buy blower motors, boards, relays, or hidden electrical parts from a no-air symptom alone.
If the page title is the only evidence, keep hidden electrical, blower, duct, refrigerant, and control parts out of the cart.
Do not ignore water, ice, breaker trips, hot smells, scraping, sharp buzzing, or equipment that will not respond to the thermostat.
Do not use any part unless the size, style, wiring, and diagnosis match your installed system.

Fast sorting table

Use this table after one controlled check and any normal startup delay.

Clue	Most likely cause	Next move
Fan On works	Blower can run	Check the normal heat or cooling call.
Fan On does nothing	Power, safety, blower, or control issue	Check visible clues and stop before internal work.
Dirty or wet filter	Airflow restriction and possible ice	Install exact filter and retest once.
Pan water or raised float	Condensate safety clue	Clear water before judging switch.
Breaker trips again	Electrical or motor fault	Keep off and call service.

Checks that actually matter

These checks keep the diagnosis tied to what you can see or safely test.

Use Fan On once and write down the result.
Confirm thermostat display, mode, setpoint, and batteries if applicable.
Inspect filter size, condition, and airflow arrow.
Look for pan water, float-switch position, and ice clues.
Stop if the next step would expose blower wiring or controls.

When a part is likely

Keep the cart narrow and buy only when the evidence points to that exact item.

Filter evidence: dirty, damp, collapsed, missing, or wrong-size filter with weak airflow, ice, or restricted return air.
Float-switch evidence: the pan and drain are dry, but the visible switch is cracked, stuck, or will not reset.
No homeowner-visible clue justifies blower motors, boards, relays, or hidden wiring parts without service testing.

Tools You May Need

These support safe visible checks, cleanup, and documentation.

Inspection flashlight

Helps when: Use it to inspect thermostat response clues, filter fit, pan water, float switch, and ice clues.

Skip it when: Skip checks that require opening blower electrical compartments, reaching into the cabinet, or working near water and controls.

Compare inspection flashlights on Amazon

Wet-dry vacuum

Helps when: Use it only at a known condensate outlet when pan water may be holding a safety switch open.

Skip it when: Skip it when the drain outlet is hidden, water is near electrical controls, or you cannot identify the condensate line.

Compare wet-dry vacuums on Amazon

Thermostat batteries

Helps when: Use them only when the thermostat display is weak or blank and the thermostat uses replaceable batteries.

Skip it when: Skip batteries when the thermostat is hard-wired with no replaceable battery compartment or the air handler has no power.

Compare thermostat batteries on Amazon

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Replacement Parts

These are the only buy-first parts that fit the visible homeowner clues.

Air handler correct-size filter: Use this when the installed filter is dirty, damp, collapsed, missing, or the wrong size and airflow is weak.
Air handler condensate float switch: Use this only after the pan and drain are dry and the visible float switch is cracked, stuck, or will not reset.

Correct-size air handler filter for no-airflow checks

Air handler correct-size filter

Helps when: Replace it when the installed filter is dirty, damp, collapsed, missing, or the wrong size and airflow is weak.

Skip it when: Skip filters that do not match the rack size, thickness, airflow arrow, and supported restriction range.

Compare air handler filters on Amazon

Air handler condensate float switch

Helps when: Consider one only after the pan and drain are dry and the visible float switch is cracked, stuck, or will not reset.

Skip it when: Skip it when water is still lifting a working switch, the drain is not clear, or the mounting style does not match.

Compare air handler condensate float switches on Amazon

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FAQ

Why is my air handler not blowing air?

Common clues include thermostat command, power, filter restriction, condensate safety, blower trouble, or controls.

Should I try Fan On?

Yes. Fan On helps separate a blower that can run from a heat or cooling call problem.

Can a dirty filter stop airflow?

A dirty or collapsed filter can severely restrict airflow and may contribute to ice or shutdown symptoms.

Can a float switch stop the air handler?

On some systems, pan water can interrupt operation. Clear the water source before replacing the switch.

Should I replace thermostat batteries?

Only if the thermostat uses replaceable batteries and the display is weak or blank.

Should I reset the breaker?

Check it once. If it trips again, keep the system off and call service.

What can I buy safely?

A correct-size filter, flashlight, wet-dry vacuum, or thermostat batteries are reasonable when the visible clues fit.

When should I call service?

Call for no response in Fan On, breaker trips, hot smell, sharp buzzing, recurring pan water, or hidden controls.

How this guide was built

Repair Riot built this page around visible homeowner checks: thermostat command, filter condition, airflow path, water, ice, noise, breaker clues, and clear stop points before hidden blower, duct, refrigerant, or control work.

U.S. Department of Energy air conditioner maintenance — supports filter, airflow, coil, and condensate-maintenance guidance
EPA Section 608 technician certification — supports leaving sealed refrigerant work to certified technicians