That all depends on what has failed. First I would need to know the model number of your warmer, as Vollrath has many hundreds of different machines. As tech’s we normally don’t just replace parts without knowing what failed and why. To just change out parts hoping to fix a problem is costly and most times doesn’t solve the problem.
I will say this, Most all food warmers have a sensor that tells the machine and operator that it has run low of water. Question is what type of sensor. Anything from a float switch to electronic conductive rods, to pressure, to temp… About Eighty percent of the time that problem is water quality and machine cleanliness. fifteen percent is a wiring problem (loose connections), and 5 percent is actually a mechanical failed part from normal usage. These percentages change drastically with abuse or miss-use. Like water quality. When was the last time it was properly cleaned and are you using distilled water?
To troubleshoot this machine you will need a knowledge of electrical equipment, some simple hand tools, and a good quality multimeter. The ability to read a schematic. There should be one within the machine.
If you can provide us with a model number, and register to the site, I will help walk you through the troubleshooting phase. Registration is important so that we can communicate in a timely fashion. It’s free and There is no outside spam.
Just to demonstrate how vast the Cayenne line is, this is just the wet product warmers/rethermalizers. After reviewing them all, They do use a common designed heater, The heater is Teflon coated with a 120 C Klixon water temp sensor limit. They all have a simple circuit containing 5 elements. A thermostat, a water level limit, a high temp limit, the heating element, and the pilot light in parallel to the water limit.
So the question is does your unit continue to heat, with water in it. If so replace the pilot light. If it does not heat with water in it, replace the temp limit. However, a high resistance across the temp limit like a loose spade connector may create a situation that the pilot is lit but still has heat with a good temp sensor..