Old fan switch was broke.

You probably want to look inside as you read this. Most of it is straightforward, except the retaining clips.

First, I turned off the breaker switch. Opening the control housing, I disconnected the two leads and wrote down their orientation (one is silver, the other copper). In my JennAir model, an orange burner light is on either side of the fan switch. The white plastic on the rear is held on by their keyhole shape - just slide them the only way they can. This gives extra working room.

Since the switch plastic was already decayed, I snapped off the whole central square unit leaving the 2 portions held onto the posts by the metal retaining clips. Using a small flathead screwdriver, I pried up the plastic remnants, working around it until the retaining clips came loose/ broke.

The new unit fit perfectly and easily. The new retaining clips needed to be worked down a small circular file to spread the centers out enough for me to work onto the retaining posts. The file was just barely bigger than the existing hole. The clips can be broken if you are too rough or work them too much. After that, I used a pair of snub nosed pliers to push the clips down the posts. They required a considerable amount of force, but they aren't going anywhere anytime soon.

Reconnect the lights, reconnect the 2 leads, and check for any loose wires from other controls and loose parts. Reseat the control housing, turn on the breaker and test.