What Does E4 Mean on AC?

Updated: Feb 19, 2024 1:02 PM

An air conditioner error code is often not a cause for worry, though it probably raises some questions. Even the best air conditioners display codes that indicate specific maintenance tasks, so the unit stays in excellent condition. Although the E4 message appears to be an error code, it’s more of a signal. The E4 display appears on all types of air conditioning units, whether it be a central, window, portable air conditioner or outdoor unit. This code tells you that the air conditioner unit is defrosting.

Key Takeaways_

  • An air conditioner will display the E4 error code because the unit needs to defrost.
  • Many reasons cause an air conditioner to defrost, such as a lack of refrigerant or an air sensor failure.
  • The unit must defrost when this code appears if the coils have become too cold and frosted.

This article gives you the answer by explaining what does E4 mean on an air conditioner and what to do if this code appears in order to resolve the issue. And if you want more information on air conditioner codes, you can check out our article explaining what E1 means on an air conditioner.

insider tip

Keep your AC user manual because, although AC error codes appear similar across brands, many of them have varying meanings.

There are multiple reasons ‌your unit might enter ‌defrost mode, but once the unit automatically turns it on, you can’t switch it to cooling mode until it’s finished. It’s important to note that an AC unit isn’t supposed to defrost very often, so something could be wrong if you notice it happening a lot or lowered cooling power.

Typically, an air conditioner enters defrost mode because it’s become too cold and the condenser coils have frosted over. That doesn’t mean you need to immediately replace the air conditioner condenser fan yet. When this happens, the unit can’t function properly, and the cooling power switches off to bring back the working temperature. A handful of reasons that this can happen to an AC unit include:

  • Lack of refrigerant
  • Damaged heat pump
  • Air sensor failure


Low refrigerant levels can damage your AC unit, so always call a professional to add more if you suspect it is needed.

Fixing the E4 Error Code

Because the reasons for a A/C entering into error code E4 can be many, you’ll have to examine the different parts of your unit to make sure that it’s in normal operating conditions. You won’t have to do anything most of the time, and this is just a routine maintenance task.

STAT: A minimum efficiency of SEER 13 is recommended, though high-efficiency ACs may be cost-effective. (source)

But if the E4 display becomes frequent, you’ll have to perform your maintenance or call an expert to examine the machine. If it’s a repeat occurrence and you’ve invested in an expensive, integrated system like the one of the best mini split systems of 2024, we highly recommend you arrange for a professional to address any issues before lasting, expensive damages occur.

What Does E4 Mean on AC? Questions (FAQ)

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