Is it possible to remove the internal part of this actuator as I suspect it maybe a internal microswitch. The fault is when selecting the HTG mode on the programmer the boiler fails to fire up, only by selecting the HW mode does both the HW & HTG come on, with the valve moving to the MID position, with no temp control from the room stat. When selecting the HTG on the programmer the valve moves to the H position but the boiler fails to fire. Having checked various voltages with a DVM the room stat reads 240 volts on the calling terminal until turning the room stat downscale it then gives a reading of 120V, after disconnecting the white wire from the valve to the the room stat the white then gives a zero volt reading. After reading previous comments from a D Hailsham on this subject he did indicate that it maybe be caused by a S2 microswitch failure used within the actuators circuitry, so is there anyway that this can be confirm without the need to drain down the system & replace the valve? If anyone can offer some advice it would be much appreciated thanks.