Turn off the gas.
Unplug the cooktop.
Lift off the burner grate.
Lift off the burner cap.
Remove the two screws that hold the burner base in place. Lift the burner base off of the cooktop to reveal the igniter assembly in the center of the burner.
Repeat Steps 3 through 5 with the other burner housed on the same side of the cooktop. Most Jenn-Air cooktop covers are in two to three sections. If your cooktop cover is all one piece, you will have to remove all four or five burner assemblies before lifting the cooktop cover.
Lift the cooktop cover.
Follow the igniter cable back to the ignition control module at the back of the cooktop.
Unscrew and remove the cover on the ignition control module.
Unplug the igniter cables. Lift the igniter assembly off of the cooktop.
Install the new igniter assembly in the opposite manner. Plug the ceramic wires in first, then place the igniter assembly in place.
Replace the igniter assembly's cover and its screws. Replace the cooktop cover. Replace the burner bases and screws. Replace the burner caps. Replace the burner grates.
Plug the cooktop back in and reopen the gas line.