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Overhead warmers are fairly simple devices. They are typically used to keep food that is ready to be served warm before it goes out on the server’s tray. Overhead warmers have three main parts:
1. Element
2. On/off switch
3. Infinite Control
Warmers come in different voltages such as 120V, 208V, and 240V, and they are made in different lengths. Always remember that it’s crucial to have the correct voltage on the unit, because severe damage can happen when the unit is introduced to the wrong voltage. There are two types of elements in most overhead warmers.
1. Cal-rod (metal) type
2. Quartz glass type.
These elements vary in wattage and length. When replacing an element, it is helpful to provide the following information to ensure you get the correct element.
1. Overall length of the warmer
2. Model Number
3. Serial number
4. Voltage
This information can be found on the name tag that is attached to the warmer.
There are two ways to determine if an element is bad:
1. Visual Inspection. On the Cal-rod element, inspect the outside for burn marks. On the quartz element, inspect the filament or wire coil inside the glass tube. If it is separated in any way, it is burnt out.
2. Continuity Testing. A continuity tester can determine if an element is defective. Remember to disconnect the power! For either element (cal-rod or quartz), first remove at least one wire connection or remove the element if it is a socket type. If you have a Multi-Tester set your tester in the continuity position and touch the leads to the element. If there is no digital read out on the display the element is no good. If you’re using a lighted tester and the light does not light up, then the element is not good. In either case, the element needs to be replaced. The element is still good if you get a digital read out or the lights does light up.
To test the on/off switch, disconnect at least one wire from the switch and perform a continuity test with the switch in the on position. If you do not get a reading, then you need to replace the on/off switch.
To test the infinite control, there are multiple wire connections on the back of the control. These wire connections are marked as follows: L1 and L2 are the power wires coming in the warmer. H1 and H2 are the connections for the element wires. On units with a pilot light there may be a HP connection or a P connection, P meaning pilot light connection. 
Disconnect at least one wire from any of the H connections and perform a continuity test across the H prongs with the control in the on position. If you did not get a reading or light it is time to replace the infinite control. On an infinite control make sure to determine if it is a screw mount or nut mount before purchasing a replacement. Screw mount controls screw into the overhead warming unit; nut mount controls bolt onto the unit.
