A jamb switch is a light switch mounted in a door and designed to activate when the door is opened and closed. Two common locations for jamb switches are car doors and refrigerator doors. These switches are used in environments where people want lights to activate instantly when people access a space, for convenience or safety reasons. Replacement jamb switches are produced by a number of manufacturers and are usually sold with other door accessories and components.
Typically, a jamb switch turns a light on when the door is opened and shuts the light off then the door is closed. It contains a small mechanical component that moves when the door does, opening and closing a circuit. Jamb switches are typically very small, as they need to fit in a compact space. The light may be controlled solely with the switch or have a manual switch option for settings where more operational control is required.
In vehicles, jamb switches activate the dome light when the door is opened to help drivers as they are entering and exiting their cars. In some models, the light stays on for a set period of time after the door is closed to provide ambient safety lighting for the driver. Refrigerators, including both floor models and walk-ins, typically use jamb switches so people can see the interior when they open up the door. Some closets and other small rooms may use a jamb switch to activate a light as the door is opened for convenience.
A door operated light switch can also be a convenient safety feature. Jamb switches may be used to turn on a discreet warning light when a door is opened to allow people managing stores and other facilities to know when and where doors are being opened. While a bell can also be used for warning, there may be reasons people want a silent warning when the door is opened, and a jamb switch can be rigged into the door to provide this.
Replacing a malfunctioning jamb switch is relatively straightforward, as long as people get the right part. Usually part of the door needs to be taken apart, usually with screws and an access plate, and the old switch can be removed and replaced. Power should be cut to the circuit before working on it for safety. If people want to install a new jamb switch, more work can be required, as it will be necessary to run wiring to the door.