Combination stove/ovens have surface burners and an oven. Some stove/oven units are quite complex. To understand how they work, let's look at the following areas:

Control panel
Gas delivery (gas units only)
Cooktop (electric units only)
Area beneath the cooktop
Interior of the oven (electric units only)
Area behind the broiler drawer (gas units only)

Control panel:
Though there are many variations of stove/oven combination units, we'll describe the most common controls and devices, their functions, and interactions they have with other components.

Thermostat
Clock
Electronic keypad
Selector switch for bake/broil/timed bake, etc.
Surface burner switches (electric units only)
Self-cleaning buttons or switches

Thermostat:
The thermostat is usually a switch right behind the knob you use to set the oven baking temperature. There's a long, thin copper tube attached to it that leads into the oven compartment. The tube senses the temperature inside the oven and signals the thermostat to provide heat.

Another type of thermostat, called an electronic/mechanical hybrid unit, has a small electronic circuit board behind the knob. It has a 4- to 6-inch sensor attached to it that protrudes into the oven. The sensor changes resistance in the electrical circuit with the change in oven temperature. The electronic clock monitors the resistance of the sensor and turns on or off the heat in the oven. When the oven reaches the temperature you set, the sensor signals the circuit board to turn off the electric or gas burner(s) in the oven.

Clock:
The clock is either electronic or mechanical. Electronic clocks have lighted, digital readouts. When either clock fails, you usually need to replace the whole clock. Mechanical clocks usually have three dials: the clock dial, a start time dial, and a stop time dial. You set the main clock to the time of day. Then, when you choose a timed-bake or self-clean cycle, the clock turns on the oven at the start time and turns it off at the stop time. The start and stop dials are for both timed baking and self cleaning.

Electronic keypad:
Some stove/ovens have a keypad for setting all oven, broiler, timed-bake, and self-cleaning times and temperatures. Touching the pad with your finger actuates a small switch in the pad, which then sends the proper command to the circuit board or clock. These keypads can't be serviced, so you usually need to replace them when a problem arises.

Selector switch for bake/broil/timed bake, etc.:
Electric and gas stove/ovens have at least one control switch for the oven/broiler. On some units, this is the same switch as the thermostat. On others it is a separate switch. If it's a separate switch, it works in conjunction with the thermostat. You set the thermostat to the cooking temperature and set the selector switch to allow bake, broil, timed bake and preheat.

Surface burner switches (electric units only):
Surface burner switches are also referred to as "infinite switches." They work in much the same way as a dimmer switch for a light in your home. When you turn the switch from low to high, you increase the electrical current flowing through the electric burner, which adjusts the temperature of the element.

Self-cleaning buttons or switches:
In addition to clock controls for the self-cleaning feature, there may also be other related devices, such as a door lock button or switch or a switch to toggle between self clean and normal bake. Most switches in self-clean cycles are used to keep the oven door locked so it can't be opened until the oven has cooled down.

Gas delivery (gas units only):
All gas stovetop burners use a similar system of gas delivery. There's one control knob for each burner. Each knob is attached to a small gas valve mounted to a main gas line or manifold. As you turn the valve on, gas flows through the valve into a "venturi" tube, which mixes the gas with air to create the proper mix for combustion. The mixture then flows into the burner itself, where the standing pilot or spark ingnitor ignites the flame. You regulate flame size by adjusting the burner control knob, which restricts the amount of gas that flows through the valve.

The oven and broiler work in a similar way. The thermostat knob may be attached to a small gas valve mounted right to a main gas line. As you turn the valve on, gas flows through the valve into a tube attached to a safety control valve. The safety control valve doesn't allow gas to flow through to the burner unless there is an ignition source available. The ignition may be provided by a standing pilot light or by an electric igniter. When gas flows and ignites, the flame stays lit until the thermostat senses the proper temperature and shuts off gas flow, usually at the safety valve.

With a digitally controlled system the clock sends the signal straight to the safety valve. Then, if the electric igniter is working properly, the safety valve opens and sends the gas to the burner, and the hot igniter ignites it. A digital system uses a small electronic sensor inside the oven to sense temperature. When the set temperature is reached, the circuitry sends a signal to turn the safety valve off, which stops the flow of gas. When the oven temperature cools slightly, the resistance of the sensor changes. This causes the circuit board to restart the heating process and re-light the burner.

The cooktop (electric units only):
Electric stove/ovens have open, coil-type burners on their cooktops. Or, the whole cooktop may be what's called a "smoothtop," where burners are mounted under glass that conducts heat to your cookware.

Coil type burners:
Cooktops usually have four to six metal burners (or heating elements). Each is a coiled sheath with a wire in the center and no moving parts. The wire becomes red hot, which heats the metal sheath by conduction, and the sheath glows red. You see this glowing when you turn on the element. The drip pans beneath coil burners catch spills and reflect heat back to your cookware.

Euro type burners:
Euro burners are solid, smooth, and 6 to 8 inches in diameter. Each has an internal coil of wire in the center and no moving parts. When the wire receives electricity, it becomes hot, which heats the solid metal surface. Although the surface of the burner doesn't glow bright red, it becomes very hot.

Smoothtop ranges:
Smoothtop ranges work similarly to coil-type burners. There is a coiled wire beneath each burner area. When electricity is applied to the wire, it glows red hot. Heat created is conducted through the glass and either radiated to the pan on the cooktop or conducted from the glass to the metal of the pan. Some smoothtop ranges also have red halogen lights to supplement the coil-type elements. These get hot immediately, to speed the burner's warm-up time.

The area beneath the cooktop:
Many cooktops with coil or gas burners can be raised for cleaning and service. Manufacturers often place the model and serial number tag for the appliance beneath the cooktop.

The interior of the oven (electric units only):
In most non-convection ovens, you can see a heating element at the bottom of the oven and the broil element at the top. Each element is a coiled metal sheath with a wire in the center and no moving parts. When electricity flows to the wire, the wire becomes red hot and heats the metal sheath by conduction. The sheath then glows red.

The area behind the broiler drawer (gas units only):
This is where the safety valve, igniter, pilot assembly, oven burner, and other components are often located. On some units, these items are under the oven floor.