Check for coolant flow in sight glass.
Turn on the manual valve switch (MV), on the load center, to manually turn on the solenoids and see if the temperature rises. If not, check voltage output on J6 connector on the load center and ensure the LEDs are on. Follow Load Center Diagnostic instructionsin system repair manual. If necessary, replace the load center board.
If voltage is present, measure the resistance of the coil, it should be 12.5 Ω. If coil is open replace coil.
If voltage is present, test the coil with screwdriver. The screwdriver should magnetically stick inside the coil. If the screwdriver sticks, then the coil is good. Replace the plunger on valve or replace the complete valve assembly.
Check fr 240 Vac on pump. If there is the correct voltage, replace circulation pump.