Abstract: A method for monitoring operational conditions of an HVAC unit and providing preventive maintenance alerts and/or troubleshooting instructions using an ordered set of causes for sensed parameters by monitoring parameters of the HVAC unit with sensors, collecting real time information and transmitting the data and analyzing the data with a processor and comparing it to a list of pre-determined data set points to determine variances from the set points and identification of one or more maintenance alerts and/or trouble events associated with variances, matching them to at least one of the events, displaying instructions to a user for resolving the event in a descending order determined by the processor of the most likely causes along with an associated solution for each cause, and providing a pre-failure solution from the stored set of instructions based on analysis of the stored data and timed sensor values.