Aprilaire Dehumidifier Error Codes

Aprilaire makes some of the best whole-home dehumidifier units out there on the market today. But sometimes things go wrong with the unit and require your attention. Most of these problems are benign, and with the right know how can be resolved quickly. Others, are more serious and might need the attention of a professional. To help you decide which your situation is, we’ve put together this breakdown of the various diagnostic codes that your Aprilaire 1820, 1830 and 1850 units can display.

Note: some of these error codes require knowledge or skill in electrical work and are not something you should undertake if you’re not completely comfortable or experienced with this kind of work. In these cases we recommend that you call a professional to come and perform the maintenance or repair work for you.


E1 - Internal RH/Temperature Sensor open or shorted

If you see the code ‘E1’ this means that the central computer of the dehumidifier is not receiving a good signal from the temperature / RH sensor. If the unit cannot get a signal, it has no way of knowing how warm or cool it is in the space.

Here’s a useful set of instructions on what steps to take when you get this code [link].

E2 – High Refrigeration Pressure

The code ‘E2’ means that the temperature of the discharge line is more than 190 degrees Fahrenheit. Usually this problem arises when the temperature of the air going into the inlet exceeds 100 degrees Fahrenheit (in other words the air is too warm to begin with) or insufficient airflow going through the dehumidifier. This issue usually corrects itself, but if you still see this error after five consecutive compressor restarts, it’s time to take action.

Here’s a useful set of instructions on what steps to take when you get this code [link].

E3 – Model 76 Remote Control Communication Loss

According to information from the manufacturer, if you see the code ‘E3’ that means that the ‘model 76 control’ has stopped communicating with your dehumidifier. If this is the case, the fix may require some electrical work. If you’re handy with that sort of thing, you can find the full instructions here [link], otherwise we recommend you call a professional to perform the maintenance. Dehumidifiers involve high voltages and it’s not really a DIY task you should undertake if you don’t feel completely comfortable.

E4 – Insufficient Capacity

Unfortunately this is not a very descriptive error code. Capacity of what? According to the manufacturer’s literature, this error code can happen when the dehumidifier is transferred from a place with cold air to a place with warm air. If that’s the case, wait an hour and then check again. If the error code is still there after re-checking in an hour, it’s time to consider troubleshooting.

E5 & E6 – Temperature Sensor Failure

When you see either E5 or E6 it means that the signal to the high temperature or low temperature sensor is shorted. According to the literature from the manufacturer, this error can arise due to a loose connection on one of the circuit boards, or a failed sensor. This fix does involve electrical tasks so if you are comfortable with that, see the instructions here [linked]. If not, call a pro (us?) to come and fix it for you. Of course, if you’re a part of our dehumidifier service program these kinds of fixes are included.

E7 – Float Switch Open

This error code E7 means that a float switch has been triggered or opened by water accumulation in a drain pan of the unit. Follow the instructions in the literature from the manufacturer [link] to remedy this issue. And if you don’t feel comfortable working with electrical equipment – leave it to the professionals!

E8 – Inlet Air Temperature or Dew Point Out of Range

This error means that the temperature of the air is below 50 degrees F or above 104 degrees F. Or, it could mean that the dew point is lower than 40 degrees F. This error most likely is happening because you have installed the dehumidifier in a space that experiences temperature extremes. The dehumidifier unit has an operating temperature range and if the temperature falls out of this range then bad things can happen. So it’s a good idea to keep the unit in a space where the temperature is not too cold or too hot. If you’re getting this error, it might be time to think about moving the unit to a different space. If it’s too hot for your unit, then move the unit into a cooler spot. If it’s too cold, maybe you can move the unit higher up where the air is warmer.

E9 - Outdoor Temperature Sensor open or shorted

This error means that the temperature registered on the outdoor temperature sensor is out of range. You should only get this error if you have enabled the ventilation feature. Aside from actual cases in which the temperature is indeed out of range, the other reason why this error might happen is a failed sensor or a loose connection. Here are the instructions for remedying this issue [link].

We hope this guide helped to inform you of the different error codes you may encounter over the life of your Aprilaire. Again, some of these errors require serious fixes that involve electrical work, and electricity can be dangerous if you don’t know what you’re doing. In these cases you should call a professional to  come and fix your dehumidifier for you.

And just a final reminder, if you have an Aprilaire dehumidifier (which we sell on our DIY store by the way) you can enroll in our maintenance service program and get regular maintenance as well as help whenever errors like this arise so you don’t even have to go down into the crawl space or basement!

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About Michael Church

Michael Church has been involved with indoor air quality since 2005 and feels the unhealthy crawl space is one of the major problems causing poor indoor air quality.


  1. Danny Marbury on August 13, 2019 at 5:10 pm

    I turned off my dehumidifier and when I tried to turn it back on it gives an E3 error code. I says to push the up and down arrows simultaneously for 3 seconds and then push the stare button. I flashes off and remote and the E3 code appears but the unit will not start up. The weird thing is I have not wired up the remote yet? Suggestions?

  2. Alex Leung on May 31, 2020 at 1:24 am

    Hi Michael,

    My dehumidifier shows the error code E4. I tried to troubleshoot, the compressor seems fine, I let it ran for 15 minutes and checked the inlet air temp and suction line temp. The suction line temp only 2 degrees lower than the inlet air temp. Some said it most likely caused by refrigerant leaks,
    If this is the case, can I just change out the part? Unfortunately, I couldn’t find anything that talks about Aprilaire refrigerant.
    Please advice.

    Thank you.

  3. Stan on December 17, 2020 at 10:12 am

    Hello, we moved in to a house in July with an Aprilaire 700 system. Now that it’s cold and the furnace is running i would like to use it. I’ve replaced the humidifier panel, ensured the unit is plugged in and the water is on. When I set the digital control to test I get the flashing green light I do not hear the Aprilaire blower start nor do I see any water in the drain tube and after about a minute I see what appears to be r1 appear on the control panel. Is that an error code? If so can you tell me what it means? I do have the HVAC blower on throughout the test. Thank you!

    • Michael Church on December 17, 2020 at 10:22 am

      Hello Stan, this is what we found in regards to that code. I would recommend you call their customer service if you need assistance in troubleshooting your model 700. (800) 334-6011, Monday through Friday, 7:00 a.m.-5:00 p.m. Central Standard Time
      “Aprilaire’s response: Thank you for contacting us regarding your model 600M humidifier. The R1 that you see on the screen after the test mode simply means the control is a revision one control. This revision indicator has no effect on the operation of the control or the humidifier.”

      • Stan on December 17, 2020 at 12:37 pm

        Ah, okay, well time for some more troubleshooting then. I appreciate your time and the response!

  4. Joe on February 18, 2021 at 11:26 pm

    Hey mike wondering if you can help me out. Display on unit is saying service required. It looks like it’s in remot mode but I only have external 76 controller wires up. It won’t let me select external option…. any ideas I unplugged unit and left turned off

  5. Zach Zimmerman on April 26, 2021 at 11:36 am

    Have an 1850 that is dripping around the outlet? Not the threaded part l. Possible clog from within? Or not enough slope? It’s gravity fed so it won’t go uphill I’m assuming. Thx for any help. Love your brand man!!

    • Michael Church on April 26, 2021 at 1:07 pm

      Thank you so much and thanks for contacting us, I am so sorry to hear that your dehumidifier is leaking. If you got the 1850 from our DIY store or if we installed it for you, please contact us at https://diy.crawlspaceninja.com/contact-us/. If not, I’d recommend contacting Aprilaire at (800) 334-6011. Hope that helps.

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