I have a Vaillant turboMAX pro that has recently been serviced. I just switched it to central heating mode but no heat is coming through to the radiators. I am getting hot water. The boiler itself is attemoting to switch to heating mode every 10 seconds or so but it keeps failing. There is no warning light on the boiler. The pressure is between 1 and 1.5 as required by the instruction manual.
