How Do I Fix My E4 Code on Dometic AC? (Thermostat E4 Code)

There is a sensor for everything. Once modern technology got involved, electronic devices got far more complicated than they should be. In many cases, there is nothing wrong with the device. It is usually one of the many sensors that have the problem and when they do, you lose the use of the device.

The E4 error code for the AC unit says-Open circuit or out-of-range Outdoor Temperature Sensor (select models). This could mean that a wire is loose, the thermostat has overheated and a reset may not solve the problem.

To learn more about this error code just continue to read our article. It explores the issue so that you get the best information possible. This is not a major repair although the worst-case scenario is you have to replace the thermostat.

Dometic Thermostat E4 Code Cause


There seems to be some disagreement as to the cause of this error code. One RV owner stated that this was the result of a non-repairable, non-serviceable refrigerant leak. But that seems highly unlikely since the code has to do with a sensor and not the refrigerant.

Another owner says the unit is iced up but that is also a little on the extreme side as well. The more realistic sources would be that there is a problem with the thermostat setting, a wire or cable is loose, or the outdoor ambient temperature sensor has gone bad.

In these cases, you would have to check the wiring to make sure it is tight, then test the sensor or have it tested, or replace/repair the thermostat. One technician said that the thermostat needs to be removed from the wall and placed in the fridge for 10 minutes.

It seems that when this device gets too hot, it triggers the E4 code. With so many different opinions, check the Dometic error code list and it will tell you that the heat pumps have been locked out.

You may need a technician to get it fixed as the Dometic website does not offer a plan of action to fix it.

How do I Fix My E4 Code on Dometic AC?


The fixes seem to be quite simple if you are not under warranty. If you go to a dealer you may not see your RV again for 3 weeks. But aside from the solutions we mentioned previously, there is one key spot to check.

Remove your air filter cover and you should see the electrical connections. These can come loose when they are not secured with the proper wire connectors. It only takes a few minutes to tighten them up with the proper connectors and a wire crimper.

However, if you are still under warranty, let the dealer or approved technician handle the problem. Sometimes the problem occurs when you put the thermostat in the wrong mode.

Just adjust the mode to have everything back to normal again. Another thing to watch out for is the outside temperature. When you are using your heat pump function, you cannot use it below 40 degrees F.

When you do, you may trigger the E4 error code. You just have to shut the heat pump mode off till it warms up. We checked the Dometic error code page and all they say is:

Open circuit or out-of-range Outdoor Temperature Sensor (select models). The heat pump and dehumidification operation will be locked out. Air conditioner, furnace, heat strip, and fan operation can continue to operate.”

There are no repair instructions given by the company for this problem.

Dometic E4 Code Reset


One owner went to test his control panel and he removed the red wire. Everything seemed to be fine and after 30 minutes he connected the red wire, and the code was gone. This may be the proper reset process to use.

Upon further investigation, this code seems to be somewhat of a ghost. It will trigger even though Dometic stopped using the outside temperature sensor. It will also trigger when you do not have a heat pump feature.

When you see the E4 code, it simply means that the heat pump feature has been locked out. The AC and furnace units should still function. When you see an E4 error code after the 2017 models, The problem lies in the control board and if you are still under warranty, you should get a replacement with no problem.

The reason Dometic stopped installing the heat pump and outdoor ambient temperature sensor was that there were not a lot of requests for the feature and the parts caused too many problems.

How this relates to resetting the code means you have to get some new parts as there does not seem to be a reset function other than what we mentioned at the beginning of this section.

2 E4 Error Codes


Dometic has put out web pages with the error codes on them. At least they provide the explanation for the codes but do not offer any repair assistance. The E4 code for the Dometic 3313192 thermostat is as we reported earlier.

However, there is a second E4 code and it is for the Dometic CCC 2 thermostat. It says the same thing except it adds that the dehumidifier feature will be locked out as well. Everything else will function.

If you see the E4 code you may have a bad thermostat and it will need to be replaced.

Some Final Words

The E4 error code seems to be valid on earlier models of Dometic AC and heat units. To fix it means doing a lot of simple things like removing wires and reconnecting them, tightening up loose connections, and letting the RV or trailer bounce around a little.

That last fix came from one owner in Mississippi. The worst-case scenario is replacing the thermostat. Then if it is too cold for your heat pump to work, it will trigger this code as well. To get the right fix, talk to a technician.

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