Upon arrival found t-stats on but air handler was not turning on. Had no hot water at air handler so the clip on aquastat was not turning the air handler on. Checked circulator pump at boiler and found the loop to be air bound and overheating the pump. Bled zone of air and the air handler clicked on to heat mode. Checked temps on supply and return pipes and had 159 supply and 146 return on the end of the heating cycle. Found that the auto feed backflow combo has to be replaced due to water still leaking by when system is at pressure and that the tridicator is stuck and not displaying pressure and temp accurately. Recommend replacing both