A crankcase heater is a small electrical heating element wrapped around the bottom of the compressor to keep the oil warm. Its main job is to prevent refrigerant from condensing into a liquid and mixing with the oil while the system is off during cold weather. This is critical for Heat Pump Condensers because liquid refrigerant in the oil can wash away lubrication and lead to a "locked" compressor. Most ACIq outdoor units come standard with these heaters to ensure a smooth start even in sub-freezing temperatures. If your heater fails, you may notice the compressor making a grinding noise upon startup after a long period of inactivity. We offer a variety of universal and OEM heaters in our Accessories-Kits collection for field upgrades. This small component is one of the best investments you can make to double the lifespan of your compressor. It acts as a cold-weather insurance policy for the most expensive part of your system.