I have moved to a house, where is Junkers water heater installed, made in year 1975. This is a gas operated water heater and it is the type which will heat water as it flows through. Problem: The heater starts to heat only if there is a large flow of water through. As soon as I try to adjust temperature at the tap (mixing cold water in and so reducing flow of the water through the heater, the heater stops working. So the result is either water which is too hot, or cold water. Questions: Is there a manual available at the web, which will explain how to adjust operation of this heater? Is it possible to tune this heater, and how? Does this heater have a thermostat, which does control the temperature of the outgoing water (which is possibly broken down)? Can anybody advise?