just replaced both timers, they now both keep time. the filter timer will turn on the pump, but the heat timer will not? even with the by pass switch on the pump will not operate the heat pump? everything esle works fine, blower, jets and pump low and high speed. what do i look at next???? thanks davidskibbe@hotmail.com

Do you have a pressure switch in, at, or near your heater manifold? If so, jump that out ONLY to verify if that is the problem. If your heat works after doing the jump, and you are confident that you have plenty of water flow, then you may be able to adjust the switch by turning the knurled knob on the switch counter-clockwise until it engages.