When a chest freezer, or any other kind of freezer for that matter, overheats, the problem can usually be traced to the compressor. But the compressor doesn't work all alone. Other mechanical issues can occur in the cooling process, perhaps involving the condenser or refrigerant, that contribute to the eventual failure of the compressor. Whether internal or external, a problem that causes the compressor to work harder than it should for an extended length of time will result in an overheated chest freezer and eventual mechanical failure.
To function properly, a compressor must get rid of the heat it pulls from inside the product compartment that it generates while going about its duty of squeezing refrigerant. The condenser is the part that dissipates heat; to accomplish this, it must be cleaned regularly of dirt buildup. As a condenser gets cluttered with dirt, the compressor must work harder to try to get rid of heat generated by the cooling process.
A compressor forced to work too hard for too long will eventually simply lock up and become nonfunctional. During this period of overwork, excessive heat is generated, resulting in an overheated chest freezer. The primary job of the compressor is to squeeze refrigerant hard enough to change it from a gas to a liquid state. This state change results in lower temperatures, which cools the air that is forced into the freezer compartment.
Most chest-type freezers with a compressor run on refrigerant. As the workhorse of the cooling process, compressors have been known to develop refrigerant leaks. Since the source of a leak is sometimes difficult to locate, technicians are occasionally tempted to simply put in more refrigerant and call it good. After all, years may pass before it actually fails. The problem with this strategy is that the leak is still there and, as refrigerant is released, a greater burden is placed on the compressor.
Not uncommonly, a chest freezer will feel somewhat warm to the touch, which is a natural byproduct of the mechanical process that cools the food inside. However, if you detect a hot odor or the sides or top of a unit become inordinately hot, your compressor is likely headed for failure. Better to preemptively deal with the problem rather than ignore it and hope for the best. A rotting freezer full of food can be nasty and expensive.