Troubleshooting Dometic 3 Button Thermostat Problems (Guide)

When resetting doesn’t work. Resetting the 3-button thermostat is one way to cure many minor ills. But sometimes the problems go deeper than that and resetting just won’t work. That is the time you have to pull the manual out to see if they cover the problem in the troubleshooting section.

The first place to look will be the thermostat itself. You need to make sure it has not failed on you before you move on to other possible problems. Depending on the failure, replacement may be your only option. But there may be other issues to tend to first.

To learn more about how to troubleshoot your Dometic 3-button thermostat, just continue to read our article. It has the information you want to know about so you can make the right repair and enjoy cool or hot air once again.

Common Dometic 3-Button Thermostat Problems


1. Voltage

To start things off, the best way to find out if there is anything wrong with the thermostat is to test its voltage. You will want to use a multimeter and test for DC voltage.

The normal range will be between 10 and 30. If it is below 10 and above 30, then you have an electrical problem.

2. The unit won’t turn on or stay on

There are different sources for this problem. It could be the bumps and vibration of the road have turned the unit off. This could be due to a button being turned off or there is a connection issue. The bumps jostle the connection and turn the AC unit off.

Or the solder holding the wires in place has become cracked due to the bumps and vibration of travel.

3. Error codes

Not all error codes will be this simple to fix. There are some that flash and tell you there is a configuration problem. This is more of a system issue than a mechanical or electrical one.

Fortunately, this is an easy problem to fix. It should only take a few minutes to do.

4. Buttons do not work

This is also a simple problem to fix because the source of the problem is very simple. When you have trouble pushing the buttons, then all that has happened is that dirt or grime has got inside and stopped their operation.

Or they may have worn out which can happen if you use those buttons a lot.

5. AC not cooling

This problem also has several sources and one is simply that you set the thermostat to high. It happens or someone forgot to change the setting once the night was over.

Another source could be that a sensor has gone bad and it is telling the AC unit the wrong information. Or there is a problem with one of the control boards. Those are just a few possibilities.

6. Loss of communication

This is a dual E1 error code. This code is telling you that the thermostat cannot talk to the other components and get your AC unit working. This problem needs to be tracked down as a wire or two may be loose or disconnected, broken, or corroded in some way.

Or one of the other components or the thermostat has gone bad. If you are under warranty do not touch the system.

Dometic Thermostat Troubleshooting


1. Voltage

A reset may help you get that voltage back in line. If not, then you may have a wiring or an electrical source problem. If the problem continues after resetting or working on the wires, etc., you may have to replace the thermostat

2. The unit won’t turn on or stay on

If it is a loose connection, then all you have to do is track the connection down and tighten it up. Make sure to check all the other connections so you do not have to repeat this step anytime soon.

If the solder is broken, simply add some more and make the connection strong again.

3. Error codes

There are about 8 error codes you have to worry about when it comes to a Dometic thermostat. Some of these do not involve a lot of expertise or skill to solve.

When you see the error codes, try resetting the thermostat. If it does reset the code, then you are good to go. If it doesn’t check your manual to see what needs to be done to make the code go away.

There will be codes that you will need to call in a professional repairman to handle.

4. Buttons not working

If the problem is the accumulation of dirt or grime, then all you have to do is take the cover off and clean the thermostat. Some compressed air should do the trick.

Or you can use a moist cloth, not wet, and wipe down the interior of the buttons to free them up again. If the buttons have worn out, you may need a replacement thermostat or at least a cover.

5. AC not cooling

The first problem you can handle yourself. All you need to do is reset the temperature level to a more comfortable and lower setting. That should have the AC unit kicking in.

The other problems would require the services of a skilled and approved repairman. They will have the necessary tools to track down the problem and be able to replace the sensor or control boards if they have gone bad.

They will also check for other issues to make sure they found the right source.

6. Loss of communication

If it is a simple loose, broken, or corroded wire, you should be able to handle the repair yourself. Just tighten or replace the wire and reset your thermostat. Also, check for other connection issues and fix those at the same time.

However, if the thermostat is broken or one of the other components has failed, you may need to replace one or all of them to get the system up and working.

However, if you are under warranty, let the approved repairman handle the diagnosing and the work.

Dometic 3 Button Thermostat Reset


The instructions are simple to follow. The only thing you have to worry about is that you would have to reset your desired temperature levels and the time after you are done. Here are the instructions:

- Ensure the thermostat is in OFF mode.

- Simultaneously, press and hold the MODE and ZONE buttons.

- The LCD will display IniT and all available zones.

- Release the two buttons.

- Press the ON/OFF button to exit the system setup.

These instructions are for the single-zone setup. For the dual-zone setup, the instructions are a bit longer:

- Turn the device ON.

- You should see the light and annunciator data.

- Press the MODE button to activate the annunciator light.

- Simultaneously, press the UP and DOWN buttons and hold them for a while.

- While holding the two buttons, use another finger to press the MODE button and release it right away. Ensure to press the button once at this time.

- After releasing the MODE button, release the UP and DOWN buttons.

- Press the MODE button again.

- The thermostat light will go out.

- The MODE will read OFF. If it does not, repeat the above steps.

- Test the system to check whether the reset has worked.

If these instructions do not do it for you, check your manual. It should have the right instructions for your model of the Dometic thermostat.

What To do If The Thermostat Does Not Turn On


This does happen from time to time and it is more of an annoyance than anything else. You can try resetting the thermostat to see if there was just a glitch. But if that doesn’t solve the problem then you need to go to the next steps.

The first step would be to check the battery inside the device. If it has lost all of its power or it was jarred loose for some reason, then the thermostat won’t turn on. A new battery or pushing the old one back into place will solve the problem.

The second step, if the battery is okay, is to check your connections. Wires can and do get loose and will cut the power to the thermostat. Tighten the wires or fix any that are damaged in some way.

Once you identify the damage, you will know how to fix those wires. The next step is to check the fuse. If it has blown it will need replacing. This is a simple task and you should be carrying spare fuses with you.

Finally, check the thermostat to see if it has broken or been damaged. This can happen accidentally through someone bumping into it. If it is broken, then replacement is your only option.

Before you replace the thermostat or do any repair work, make sure your warranty allows you to handle these problems. If not, call the repairman so you do not void that warranty.

How To Tell If Your Thermostat Has Failed


Since this system is not a very complicated piece of equipment, you should be able to tell if your thermostat has failed before you start any work on it. Here are some signs that tell you that it is the thermostat that is the problem.

1. The thermostat setting not matching the temperature in the room- this problem usually means that the device is not sending the right signal or information to the control panel, etc.

To confirm this is the problem, you will have to use a second thermometer to get an accurate room temperature reading. If the readings are not the same, then you need a new thermostat.

Or maybe a skilled repairman to fix the problem.

2. The display screen is blank- the battery could be dead or the fuse blew so you should check those items first before assuming that the thermostat is bad. If those parts are okay and the breaker has not tripped, then you can conclude there is a problem with the thermostat.

To determine the exact problem, call in a repairman and when you do, tell them the model of the thermostat in your RV or trailer. That way they can bring the right parts with them when they come.

Most likely, a replacement will be your only option if nothing in the wiring is wrong.

3. AC or furnace does not turn on- this happens a lot and you should check the power supply and fuses first before concluding it is the thermostat. Also, check any wiring especially if you know both appliances are in top working order.

Before assuming it is the thermostat, raise or lower the temperature setting to make sure there was no user error involved. Go about 10 degrees in both directions to confirm that the thermostat is bad.

If it is bad, then buy a replacement model and have it installed. Or let the repairman do the work for you.

Download The Dometic 3 Button Thermostat Manual


The first place to go is direct to the Dometic website. They have a document database you can use to access and download the manual you need. Just click here to get to that web page.

Or you can go to our go-to website for manuals and get a copy from them. Just click here to access one of the manuals it has on its website. There is more than one at this website so you may need to check around to find your exact model’s manual.

Some Final Words

Troubleshooting your Dometic thermostat is not a hard task. With only 8 error codes you should be able to find the source of the problem fairly easily. Some problems are very minor and only require a simple reset to fix the issue.

Other problems may require the skill and training of a top and approved repairman. When you are dealing with repairs, make sure you are not under warranty if you want to do the work.

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