Pull down on the lever, if the lever goes all the way down with no resistance, the problem you are having is not with the zone valve. If there is resistance, and you have 24 volts at terminals 1 and 2 and you have waited at least 2 minutes, the power head and or the whole zone valve is defective and needs to be replaced, Danger Removing a hot power head can be dangerous. Make sure The power to the zone valve is off, and has been off for at lease 2 minutes. Just turning the power switch off does not mean the power to the zone valve is off. Remove the top (#1) wire if you are not sure. Make sure you wait 2 minutes before you proceed. If there is enough slack in the wires, grab the head and turn it 1/8th of a turn clockwise, and lift, put the new head in by doing the reverse, Then move the wires to the new head. If the new head burns out soon after you have replaced it, you will need to replace the whole zone valve.