A Combination thermostat, sometimes referred to as a Dual Thermostat, is merely a gas thermostat and an electric thermostat incorporated into one component and sharing one capillary tube. The end of the capillary tube is mounted inside the refrigerator and senses its temperature. To better understand the graphic below, see the Electric Thermostat and Gas Thermostat pages. If the combination thermostat you are working with is the Sourdillon control, read this page and then go to Sourdillon Control.

The fact that two functions are combined into one component can create some confusion when troubleshooting. It's possible for one side of the thermostat to go bad independently of the other. It's also possible, if there is a problem with the thermostat mechanics, for both the gas and electric modes not to function, resulting in no cooling. Keep this in mind and don't jump directly to the cooling unit as the problem, if there is no cooling. Hot wiring the heat element will tell you a lot.

The Ranco combination thermostat used by Dometic and Norcold is shown below: