Duo Therm Thermostat Wiring Diagram (How To Wire a Duo Therm)

It may be an upgrade and nicer to have a modern thermostat running your AC unit, etc., but sometimes the new thermostats do not work with old wiring. Sometimes you just have to replace an old thermostat with the same model.

New thermostats may need a control / relay box to make the right connections and to operate the fan. Also, they need 12vdc power while an older RV may only provide 12vac. To upgrade to meet the new requirements can be costly.

To see a wiring diagram for the Duo Therm wiring just continue to read our article. It will link to several websites that have the diagram as well as other ones you may need to look at. But if you are not an electrician then maybe you should leave the wiring to the pros.

Duo Therm Thermostat Wiring Diagram

The following diagram is just one of the many we saw on two different websites. This was the clearest image we could get and after the diagram, we will link to those websites as there may be differences in the wiring for different eras of RVs and models.

Duo Therm Thermostat Wiring Diagram

You can find this diagram at this link, along with several other wiring diagrams. This link takes you to another website that includes the wiring diagram for the 1988 to 98 GM-C/K series.

The second website also has a very clear image of the Duo Therm thermostat showing you exactly where the wires should go. There should be no confusion when you look at that image.

Duo Therm Dometic RV Thermostat Wiring Diagram

When you go do an internet search using the above subheading as your search words, you will find a myriad of different wiring diagram images pop up. The one below is only one example of what you can find in the image results.

Duo Therm Thermostat Wiring Diagram 2

This may work for you or you may need one of the other images found on that results page. Or you can check your manual and see the wiring diagram inside of it. Usually, owner’s manuals have a good wiring diagram inside to make sure your know where all the wires go when you make this repair yourself.

How To Wire a Duo Therm Thermostat


As you will see by the image at the second link above, all colored wires attach or connect to the same color wire on the other end. Do not cross those wires or your new thermostat won’t work

If you look at the different diagrams at the first link above, you will see that gray and brown are the only exceptions to that rule. These colored wires connect to each other. Also, you may see that one white connection is left empty.

Other than that, wiring a Duo Therm thermostat is just regular wiring. Connect the wires to the right places and you are done. This task should not take very long to do and if you go one wire at a time it will be over before you know it.

Some Wiring Tips For The Duo Therm Thermostat


If you are doing this for the first time, it pays to get some tips from the pros. Those tips will help you save time and avoid mistakes that can delay your completion or damage your thermostat.

1. Make sure the power is off- whenever you work with electricity, always turn the power off. Even little devices like this can provide you with a shock. And if you make a wrong connection, having the power on could damage the thermostat.

2. Use the right tools- in this case, a flathead screwdriver may be the only tool you will need. But it pays to have a multimeter on hand to test the wires once you have made the connections. You will need to see that the right amount of power is running to the thermostat.

If there isn’t then you need to track down the problem and fix it before you are done.

3. Make sure you know which wire goes where- it has been said that the Duo Therm thermostat may not follow conventional wiring codes. If true, this makes it difficult to put the right wires into their correct spot. White is neutral and black can be hot depending on the wiring system.

4. Have the wires longer than you need- this is an essential move no matter what type of wiring or construction work you are doing. You can always remove extra wire but it is risky to add more wire to the system.

Give yourself some working room so you can connect the wires easily.

5. Do a test- when you think you are done, always test the wires and voltage. Make sure everything is at the right power level and that the electricity is flowing as it should.

If it isn’t trace your steps to find your mistake and correct it.

6. Find a tutorial- this may help you as visual is often better than written. You can see what needs to be done and how to do it. Sometimes words on a page are just not enough.

Or find an old pro to help guide you as you do the work. Experience always pays off especially when something was not connected right.

Don’t forget to use top-quality wires, parts, and products. They may be more expensive initially but they generally tend to last a lot longer than the lower-quality products.

Some Final Words

Wiring your new Duo Therm thermostat in to replace your old one may not always work. The older thermostats never needed the parts that the new models need.

The good news for owners of older RVs is that many of those older thermostats are still being made today. Just use the part number to find one and your wiring worries are over.

The Duo Therm thermostat may be good, but it does not always work in all RVs or trailers.

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