What Does E1 Code Mean On a Dometic Thermostat? (How To Fix)

The more things change and get upgraded, the more complicated the device can become. What used to be a simple fix, may take skilled fingers, a trained mind, and lots of references to get the job done right. The Dometic thermostat is one such device.

The E1 error code is indicating that one of the 4 cables used to connect the thermostat to the dual AC CCC2 system has lost communication with a sensor or control board. You may also get it if there is a problem with the Penguin II control board.

To learn more about this error code and what it means, just continue to read our article. It has the information you want to know about so you can make the proper repairs or know when to call in a technician to do it for you.

E1 Code on Dometic Thermostats


If you do not have an owner’s or instruction manual for this feature, then the following information should be helpful to you. The E1 code is about communication or disrupted communication.

Those communication lines run between the front and rear sensors as well as the front and rear control boards. But that is not the only problem the E1 code is alerting you to. It could also be that the Dometic Penguin II AC control board has a problem.

Diagnosing the exact problem takes a little skill and a little time as the location of the RJ11 cables and connectors may not be in an easy-to-access location.

You should know your stuff as while the error code does indicate a problem with the thermostat, it may not be indicating a problem at that particular time. The trouble could lie elsewhere.

The way to eliminate the thermostat is to check to see if one zone is operating from the thermostat. If it is, then the thermostat is not the problem nor are the RJ11 cables.

What Does E1 Mean On a Dometic Thermostat?


The meaning of this code is that, one, the main control board has a problem and you may need a technician to help you fix it. Or it may mean that there is some corrosion somewhere the cables connect to other components and communication is interrupted.

To exclude the corrosion possibility, you would have to access where each cable is connected, both sides, and then clean and reinsert them into their ports. To access some of those ports, you have to get on the roof of your RV or trailer and remove the AC cover.

Then you have to remove the control board cover and the control board for the best access and freedom of movement. But these are not the only connections you have to deal with. You also have to go to the front and rear intakes and remove the RJ11 plugs at those locations as well.

If there is no corrosion, you still have to check to see if these cables are faulty or not. That takes good equipment you may not have. You have to test all 4 connections individually to find out which one is bad.

Two of the tools you would need would be an RJ11 crimping tool and an RJ11 tester. This is just the start as the next section continues with the repair work that is possible for this problem.

How To Fix E1 Code On a Dometic Thermostat


If your tests of the RJ11 cables did not solve your problem or even found it, then you need to move on. You should swap out the front and rear control boards. The swap means removing connections and putting them back into their correct spots on the other control board.

If you find the faulty zone with this swap, all you have to do is change the old control board for a new one. At this time, you may have to adjust the dip switches. This is something you do not do during the swap.

During the swap make sure you are on battery disconnect, breakers are turned off and you are not connected to shore power. Also, part no. 3312022 supersedes and replaces 3312227, they are supposed to be the same part.

If you have to reinitialize the system, you only need 12-volt power to both the rear and front AC units and the thermostat. It has been confirmed that you do not need to be connected to 50 -amp shore power to do the reinitialization process.

Also, you may find an extra RJ11 plug inside the rear intake. Do not worry about it or connect it up. It is not being used. Then the control boards may not be in stock but are on back order right now.

Dometic E1 Code Reset


The following information comes from the Dometic Thermostat Troubleshooting Guide:

E1 Error Code: What Does It Mean and How to Fix

An E1 error code could mean the Dometic thermostat has lost connection to one or more of the power circuit panels. To clear this error, try the following workarounds:

- Reset the thermostat Dometic thermostat. Check to see if it works.

- Reset the Dometic power fuse. If this does not resolve the problem, proceed to the next step.

- Switch off and on the main power circuit breakers.

If those do not work, then you should call in a Dometic specialist to handle the repair and do the resetting for you.

Some Final Words

When you own an RV or trailer with a lot of modern features, you can expect the repair work to be on another level. While you can do many of the repairs to these modern features, you may not have the tools or the know-how to make the repair.

It may be best to let the pros handle the work on a Dometic thermostat unless the problem is very simple and does not require special tools or knowledge. They will get the system up and running for you.

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