Why is there no warm air in Futian pickup truck?

There is a switch on the heating pipe in the engine room. Isn't it open? Then start the car, wait for the water temperature to come up, and try by hand whether the two warm water pipes from the engine room to the cab are the same temperature. If the temperature is the same. This is the panel switch. If the temperatures are different

It is possible that the circulation of the warm air tank is not good or blocked.