What is the principle of car parking heater?

What is the principle of car parking heater? After reading the schematic diagram, I found that it is so simple to broadcast the article

There are two types of car parking heaters, one for preheating the coolant (heating liquid) and the other for heating (heating air).

The parking heater for preheating the coolant is also known as the "diesel stove". It is specially designed to solve the problem that the vehicle is difficult to start at low temperature. The vehicle is easy to start and the wear caused by cold start is avoided. Most of them are installed on diesel vehicles. For example, pick-up trucks, trucks, diesel SUVs, construction machinery, etc. can increase the coolant temperature after the installation of parking preheating, and the vehicle is easier to start.

The heater used for heating is also called "firewood heating", which is specially used to solve the problem of insufficient hot air and low temperature in the air conditioner in the vehicle, and the problem of heating in the vehicle after the ignition is turned off. The heat source of automobile warm air comes from the waste heat of the engine. When the engine water temperature is insufficient, it is difficult to raise the temperature in the vehicle, or there is no warm air after the vehicle is turned off. At this time, the diesel warm air can play its part!