To replace a Honeywell zone valve, first turn off the power and water feed to the broiler, and turn the two shutoff valves from each side of the zone valve to the Off position. Before removing anything, take a photo of the wiring, and write down where each wire connects. Locate the connection point on the zone valve head between the zone valve body and the piping connections. Remove the connector tab by pushing it and twisting it counter clockwise.
Once removed, prepare for some water to drip from the valve. Leave the valve connected to the wires while you connect the new valve head to the original valve body. Turn the valve head clockwise to secure it until you feel it click into place.
Once the new valve head is in place, remove each wire from the old valve head one at a time, placing each one onto the corresponding terminal on the new valve head. Reconnect the water, and check the shut-off valve. Turn the power back on, and check the broiler to ensure it is working.
Keep the photo of the wires and the list of wire connections handy during the install in case any of the wires disconnect before you are ready to move them. If the body of the valve needs to be replaced, solder the pipes, drain the boiler, and purge air from the lines before removing the original. Many times, the head is the only part that needs to be replaced. When replacing the valve, try to find the same model part, which facilitates an easy installation.