Abstract: A heating plant monitor system for visually signalling the presence and location of a malfunction or abnormal condition is disclosed. The system is particularly adapted for use with residential or mobile home heating systems and includes a visual display panel with indicator lights with each indicator light corresponding to a particular system condition or component to be monitored. The arrangement of the light sequence on the panel corresponds to the order in which each component should be checked by a serviceman so that the condition of the entire panel, when one or more malfunctions occurs, will indicate which component should first be checked for malfunction and which other components need not be inspected. Other household components, spaces or services can also be monitored for the presence of an operating abnormality or for water, smoke, etc., by adding monitors and indicator lights to the basic heating plant system.