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True Trade Path

Diagnostic guide

Outdoor AC Unit Not Running

Indoor fan runs but the condenser stays silent — check disconnect, breaker, thermostat call, and contactor before assuming compressor failure.

System
Cooling
Causes covered
7
You can check
3 without a technician

Stop and read this first

  • Do not bypass safety switches to force outdoor run.
  • 240V in disconnect — qualified work only beyond visual checks.

Work through these in order

Ordered from most to least likely. Working top down means you rule out the cheap, common causes before paying anyone to look at the expensive, rare ones.

  1. Tripped breaker or blown fuse in disconnect

    CommonYou can check
    How to check
    Outdoor dead; indoor blower on.
    The fix
    Reset once; if repeats, call tech.

  2. Thermostat not calling for cool

    CommonYou can check
    How to check
    Mode heat or fan only. Batteries dead.
    The fix
    Set cool below room temp; replace batteries.

  3. Failed contactor

    CommonNeeds a pro
    How to check
    No 24V click outdoors. Contacts pitted.
    The fix
    Replace contactor ($150 to $300).

  4. Failed capacitor

    CommonNeeds a pro
    How to check
    Hum outdoors but fan does not spin.
    The fix
    Replace capacitor ($150 to $350).

  5. High or low pressure switch lockout

    CommonNeeds a pro
    How to check
    Unit ran then stopped in extreme heat.
    The fix
    Tech resets after finding root cause.

  6. Condensate overflow switch tripped (attic/furnace)

    PossibleYou can check
    How to check
    Pan full shuts whole system.
    The fix
    Clear drain and reset switch.

  7. Seized compressor

    UncommonNeeds a pro
    How to check
    Hums loudly then trips breaker.
    The fix
    Compressor or system replacement ($3,500 to $12,000).

Direct answer

Indoor blower on but outdoor silent — check breaker, disconnect, thermostat call, then contactor and capacitor before assuming dead compressor.

Severity and urgency

Fix within days

No cooling in heat waves; compressor damage if misdiagnosed.

Cost of ignoring it

Compressor $1,500–$2,800; contactor $150–$300 fix.

How a pro will diagnose it

Verify 24V call, test capacitor/contactor ($99–$179 diag).

Prevention and maintenance

  • Replace filter
  • Keep disconnect accessible
  • One breaker reset only
  • Thermostat batteries yearly
  • Annual electrical check

For trade owners

Pricing this job as a contractor?

Homeowners see national ranges on this page. If you are building the estimate, use the same scope assumptions — then price to burdened labor, overhead recovery and a real margin.

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Find a licensed pro

When you are ready to hire for outdoor ac unit not running, start with licence verification — not with whoever answered first.

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Common questions

Could tripped breaker or blown fuse in disconnect be causing this?
Outdoor dead; indoor blower on. Reset once; if repeats, call tech.
Could thermostat not calling for cool be causing this?
Mode heat or fan only. Batteries dead. Set cool below room temp; replace batteries.
Could failed contactor be causing this?
No 24V click outdoors. Contacts pitted. Replace contactor ($150 to $300).
Could failed capacitor be causing this?
Hum outdoors but fan does not spin. Replace capacitor ($150 to $350).
What is the most common cause of outdoor AC not running?
Check disconnect fuse.
Can I fix outdoor AC not running myself?
Some checks are DIY-safe (shutoffs, filters, simple adjustments). Licensed HVAC technician work is required when gas, sewer, refrigerant, or main lines are involved.
How much does professional repair for outdoor AC not running cost?
Contactor $150–$300; capacitor $150–$350.
How urgent is outdoor AC not running?
Burning smell — shut breaker.
Should I shut off water or power for outdoor AC not running?
Shut off the local supply or breaker when leaks, flooding, sparks, or gas odor are present. If unsure, stop using the system and call a pro.
Will outdoor AC not running damage my home if I wait?
Moisture-related issues can rot framing and grow mold within 48 hours. Mechanical issues often worsen — seized pumps, cracked heat exchangers, or compressor damage cost far more when delayed.
What should I tell the HVAC technician on the phone?
Describe when it started, what changed (weather, remodel, new appliance), what you already tried, and whether multiple fixtures or zones are affected.
Does homeowners insurance cover outdoor AC not running?
Sudden pipe bursts are often covered; slow leaks, maintenance neglect, and sewer backups frequently are not. Document with photos and read your policy endorsements.
How do I know the quote for outdoor AC not running is fair?
Get two written quotes with scope, parts, warranty, and permit line items. Compare to regional mid-range pricing — not the cheapest emergency rate.
How can I prevent outdoor AC not running from coming back?
Follow the prevention steps on this page: maintenance schedules, avoiding grease and wipes in drains, filter changes, and annual tune-ups where applicable.

Once you know what it is

Step one

Know what it should cost

Get the range before you call, so the first number you hear is not the only number you have.

Step two

Decide repair or replace

On equipment near end of life, the repair is usually the first of several.

Step three

Check the quote

Compare against the typical range and confirm the terms before you sign.

HVAC System Replacement cost guideRepair or replace calculatorEstimate repair costAnalyze a quote

What the fix costs

Tools for this decision

Other symptoms