Said It Here

Why does my HVAC fan run continuously and blow hot air?

The HVAC fan can run constantly during hot weather because of a stuck relay, a faulty control board, or a short in the wiring at the main unit rather than an issue with the thermostat. This failure prevents homeowners from shutting off the blower from inside the house, often forcing them to cut power to the system entirely.

What people tried

Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.

  1. 1
    disconnecting power to the system
  2. 2
    Tracing voltage with a multimeter to locate the source
  3. 3
    Checking for a bad board or open limit switch
  4. 4
    Buying an exact model replacement part for a plug-and-play fix
  5. 5
    Calling a professional service technician

In their words

Unedited, most upvoted first, each linked to the thread it came from.

“I never did anything with AC units before and had no clue what I was looking at.”source ↗

“Contactor was welded and wouldn’t release. Fan and compressor just kept running forever.”source ↗

omegafrogpoop · r/hvacadvice · 7 upvotes

“Our HVAC system starts blowing hot air through the vents during hot weather, and there's no way for us to turn it off unless we disconnect some power”source ↗

“We replaced our antique thermostat with a Nest, but it’s still doing the same thing”source ↗

Realistic-Tie9678 · r/hvacadvice · 2 upvotes

“Recently the air blower runs almost constantly.”source ↗

“I disconnected the thermostat and the fan continues so I think I have it narrowed down to something in the main unit.”source ↗

Chemical-Ad-3461 · r/hvacadvice · 1 upvotes

Where this came up

r/hvacadviceair conditioningappliance repairapplianceshome maintenancehvachvac repairthermostat

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