Dometic Thermostat Not Working? Try These Troubleshooting Tricks For A/C and Furnace

Dometic thermostats are generally pretty reliable, but they may start acting up every now and then. If your thermostat isn’t working correctly, don’t panic. You can try a few things to get it back up and running.

We’ll walk you through some of the most common troubleshooting tricks for fixing a Dometic thermostat. Keep reading to find out more.

What Is a Dometic Thermostat? 

A Dometic thermostat is a device that helps regulate the temperature inside an RV, camper, or boat. It senses the ambient temperature and then sends a signal to the heating or cooling system to turn on or off as needed. While there are many brands of thermostats on the market, Dometic is a very common brand name to see in RVs and boats supplying everything from toilets and fridges to awnings and coolers. Two out of the three RVs we’ve owned have had Dometic thermostats in them.

Most Dometic thermostats have a range of settings you can use to customize the temperature regulation, such as the fan speed. Some Dometic units even have a dehumidify setting, which you may find particularly useful in boats.

How To Use a Dometic RV or Boat Thermostat

Dometic Thermostats are usually pretty intuitive for basic changing of Modes and degrees, but when you get into troubleshooting or resetting they can be tricky. Over the years Dometic has tried to minimalize and streamline their thermostats to look sleek and modern, reducing the number of buttons on them.

Generally, the MODE button will cycle through the various functions your thermostat controls. You’ll see Cool, Heat, Heat Pump, and Fan Only cycle across the screen, depending on the model of the thermostat. There are usually 3 fan settings that you can select: Auto, Low, and High. Auto Fan will switch between low and high depending on the temperature difference of the RV and what you’ve set. Many Dometic thermostats also have timers so you can program them to turn on and off at certain times.

It is handy to have your Dometic thermostat manual to look up program settings and more. You should have this in your RV or boat documentation upon purchase. If it is hiding from you, you can likely find an online version of your manual. First, look up what model your thermostat is. This should be somewhere on your device. You may also be able to match it to the pictures or manuals available on Dometic’s website.

Why Is My Dometic Thermostat Not Working? 

You may have several culprits that could cause your Dometic thermostat to stop working. Physical components on the thermostat can fail. Design flaws can cause a thermostat to work erratically. Low or no power can also cause it to fail. Fortunately, most handy folks can troubleshoot and even fix a large number of common issues.

How Long Do Dometic Thermostats Last?

Fortunately, thermostats don’t have an expiration date. They just work until they don’t. But most Dometic thermostats work for at least 10-15 years. That doesn’t mean they can’t go bad sooner.

Old or improper wiring can cause a thermostat to wear out quicker than it should. Too much dust build-up can shorten its lifespan. Not changing out the batteries regularly can also put stress on a thermostat. These all can cause a thermostat to expire prematurely. 

Pro Tip: We found the 5 Best RV Thermostats and broke down how to use them in your RV.

Try These Troubleshooting Tricks to Get Your Dometic Thermostat Working Again

Though your Dometic thermostat may not function properly, that doesn’t necessarily mean you need to replace it. Many things can go wrong, but you also have many ways to fix them. You just need a little knowledge to troubleshoot and fix many thermostat issues. Let’s look at some of the more common ones.

Check For Power

The number one reason a Dometic thermostat is not working is because of a power problem. This may seem simple but since RVs utilize multiple power sources, be sure that your furnace or air conditioners have power.

More than once a breaker tripped on us and the AC quit working even though the thermostat was commanding it on. If your battery voltage is low the furnace might cut out as well. Check your battery charger to make sure it’s providing enough DC voltage and if running the air conditioner, make sure its getting AC power.

Check the Specific Error Code

Most newer Dometic thermostats have a digital display. Aside from helping set the temperature and other controls, these displays also provide error codes to assist in troubleshooting.

Most of the errors deal with communications, sensors, and zone configuration. While this may sound complicated, the good news is that resetting the thermostat will often clear the problem. If the error code persists after a reset, you will need to dig into the trouble a bit more but it might point you in the right direction.

Check the Thermostat Power

If you have a digital display that is not displaying correctly, first ensure it is getting power to the thermostat. Remove the cover and check the DC voltage to the thermostat panel.

There are two types of Dometic thermostats, one uses standard wiring, and the other uses a comms cable. If the unit has wiring, use a multimeter set to DC, and apply the red probe to your thermostat’s red wire (positive). Simultaneously apply the black probe to the black wire (negative). It should have about 12 Volts. If it isn’t at least more than 10 volts, you may have a power issue or need a new thermostat.

If the unit has a comms cable, you will need to check the wiring at the device it comes from, usually the furnace or air conditioner. You may need to test the cable as well but if you don’t know how to do this you should probably call a professional.

Look for Cracks on the Solder Joints

Especially on older units, but even on newer ones, a bad connection can cause confusing issues, such as the unit shutting off midstream or working intermittently. This usually results from a cracked or broken solder joint on the switch or other elements.

You can easily repair this with an inexpensive soldering iron kit. Just be careful not to touch other components when fixing a cracked solder joint. However, a repaired joint can last for years.

Clean the Buttons 

RVs and boats get dirty. RVs, in particular, can get extremely dusty, allowing dirt and grime to make their way into the control panel around and behind the buttons. 

Remove the thermostat cover and clean around the switches and buttons. Then use a small screwdriver to pry off the buttons. Underneath, you’ll see contact points you should clean with a specialized cleaning solution and a cotton swab.

If you have a newer touch-sensitive thermostat (no distinct buttons), the foam that transfers your touch on the back of the face plate may have compressed over repeated use. This may make it difficult to change the temperature setting or switch between modes. You can try adding material to the back of the foam to restore its original thickness, or replace the face plate. Be sure to check your warranty paperwork for the Dometic thermostat to see if it is covered.

Pro Tip: RV heating up? Find out How to Troubleshoot and Repair Your RV Air Conditioner.

How Do You Reset Your Dometic Thermostat?

The reset procedure returns your Dometic thermostat to its default factory settings. This can fix any number of issues with it. A system reset is a good first troubleshooting step if you have inconsistent issues, display irregularities, or general malfunctions. This often fixes such problems.

Always follow the manufacturer’s specific reset procedure. Thermostats have a general reset procedure, but specific models can have variations.

For a single-zone Dometic thermostat, initiate the procedure by turning it off. Then simultaneously press and hold the (+) button and the On/Off Mode button for at least 3 seconds. The display will show a (–) symbol. Press the On/Off Mode button again to complete the procedure.

The reset process for a Dometic 5 button-thermostat is similar. Begin by switching the thermostat off. Simultaneously press and hold the Zone and Mode buttons and return the switch to the on position. The letters FF will appear on the display. Once they do, release the Zone and Mode buttons to complete the procedure.

Remember, this is a factory reset, so any settings you may have saved before beginning the reset process will revert to the thermostat’s default settings.

If Your Thermostat Starts Working, But Your AC or Furnace Still Isn’t Working?

Maybe the thermostat wasn’t the problem? Well, if you’re still having issues with your air conditioner or furnace, we have some other articles for you to check out. We know firsthand that air conditioners have a lot of electrical and mechanical components that can trigger an error, and it helps to know how to troubleshoot and repair them quickly. We’ve also been there in the cold when your RV furnace decides to act weird, and have used these troubleshooting tricks.

Can You Fix a Dometic Thermostat Yourself?

Overall, if you have trouble with your Dometic thermostat, the first thing you should try is the reset procedure. This can often clear up any problems you might experience.

If that doesn’t work, you can try a few other things before calling in a professional. We’ve outlined these troubleshooting tips for you, so hopefully, you won’t have to spend too much time trying to fix your thermostat.

Have you tried any of these techniques? Let us know how they worked for you in the comments section below.

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