Grant Combi MK2 faulty air pressure switch

Hi All,

My Grant Combi Mk2 Boiler works well until I went away for three days. When I came back & switch on the boiler, it does not ignite. After constant tries, it fires eventually. I have replaced a circuit board, however I am facing the same issue again. Apart from this, sometimes it cycles off & on randomly. What is the problem & how should I address it?

Thanks a lot , Ian

Hi Ian,

I guess it is due to a faulty air pressure switch but it is vital to note that airflow of any type can cause an air pressure switch to not let your boiler to fire. However, it does not mean that air pressure switch is a culprit. For example, your boiler can also not fire due to broken PCB, faulty fan and the blocked flue. When your boiler’s air pressure device has wiring problems, it is possible that its communication with a PCB would be intermittent. As a result, your boiler will cycles off & on occasionally. On a safe side, it is better to call a Gas safe engineer to address the problem systematically.