What best describes the system's problem?  If more than one of the following symptoms seem to be present, they may relate to the same problem or there might be more than one problem to troubleshoot.  This might then require multiple runs through SDHW-PROB.  So, to start, select just one symptom and let's see if we can solve at least one problem and then, if necessary, come back and consider the next system problem.

Higher than normal utility bills

There is a temperature problem

The collector panels don't look right

There is a noise problem

There is evidence of a leak

The system seems to run at odd times, if at all

The controller lights don't seem right

There seems to be a pressure problem