I turned my AC on 3 days ago but forgot to take off outside cover. Discovered this when my house wasn’t cooling down.
Have I ruined my AC unit?

  • 8
    Is it working/cooling now with the cover off? If so, then probably okay. If not then ruined.
    – crip659
    Commented Jun 8 at 22:04
  • 2
    what is this question asking? ... Didn’t seem to be cooling house so I went outside and found cover on?
    – jsotola
    Commented Jun 8 at 22:08
  • 7
    Have you tried removing the cover and running the system? That's the best way to figure out whether it is ruined. If you did try, please edit your question and include more details about what you notice when it runs (blower inside works or doesn't; fan outside works or doesn't; any strange noises; whether the discharge air off the outdoor unit is notably warmer than ambient outdoor air).
    – Greg Hill
    Commented Jun 8 at 22:33

4 Answers 4


Highly unlikely

This deserves some more explanation. Your AC works by taking refrigerant and compressing it. The compressor is noisy and lives in that outside housing for that reason. The compressed refrigerant is sent to the inside unit, which has coils that allow the refrigerant to expand. When it expands, it absorbs heat, causing the coils to cool down. A blower pulls air from inside and pushes it over the coils, cooling the air.

The refrigerant then returns to the compressor, where it is squeezed. It's now hotter than the outside air, so it's pushed through coils outside, where the air cools this refrigerant back down. This is the part you inhibited. As with the inside, a fan pulls air over the coils to cool them off faster. Then the refrigerant goes back inside and it starts the cycle over.

Your cover did two things

  1. Trapped the heat next to the coils
  2. Limited the air flow of the coil fan.

Neither is good, but neither will inherently harm your HVAC. What this does, on a practical level, is prevent the bulk of the absorbed heat from leaving the system. Thus your compressor only gets some compression, and you get some cooling, but not enough. As you're not getting proper heat exhaustion, your thermostat will never reach the shutoff temperature, and thus your HVAC will not turn off.

Keep in mind, your HVAC is designed to run for long periods. If you have a hot house and like it very cold, it will have to work harder to keep it colder (especially in summer heat). This does increase the "wear and tear" on your system to have it run inefficiently for three days straight, but is unlikely to shorten the life of any of your components, beyond what normal use would provide.

In other words, you probably ran a week's worth of HVAC in three days. So if you had, say, 20,000 hours of life from your compressor, you burned about 72 of them needlessly.


If it's no longer working, then yes.

If it's still working, then no.


To your question Have I ruined my AC unit

Probably not

You just inhibited a function, of the outside unit to blow off the heat from the coil, consequently the coolant newer reached the temperature required to cool.


Blocking the heat exchange at the evaporator will make the compressor intake hotter, the compressor discharge even hotter and the pressures everywhere in the system higher.

A sane A/C system should have an overheat protection that will cut off the compressor and wait until the temperature goes back to normal.

What will happen if the overheat protection fails? The compressor will run until either of the following:

  • the pressure rises above the weakest part capability and the refrigerant finds its way to the atmosphere (usually, but not always, evident by the smell).
  • the compressor motor burns (evident by the tripped breaker, the compressor making no noise or the compressor making unuusual noises)

(both may happen in some cases)

If you do get cooling, it is highly likely that nothing of the above happened.

Forcing the system into overheat condition shortens its usable life somewhat, but this is not "ruining it".

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