The answer to 'why is my pressure regulator no hot water' is that a faulty or malfunctioning pressure regulator can cause a loss of hot water pressure or no hot water at all. The pressure regulator is responsible for controlling the water pressure entering your home, and if it's not working properly, it can disrupt the flow of hot water from your water heater.
Some common causes of a pressure regulator issue include a buildup of mineral deposits, a broken spring, or a worn-out diaphragm. This can lead to symptoms like low water pressure, fluctuating pressure, or a complete loss of hot water. In some cases, the pressure regulator may need to be replaced, which is typically a job best left to a professional plumber.