The main control knobs allow you to adjust the flow of gas to each burner on your barbecue. There is one knob for each valve. The knobs are made of plastic and attach to the valve stems on the manifold. The plastic can eventually wear, so the knob rotates, but it doesn't adjust the valve. The knobs also can become loose, so they won't to stay attached to the valve stems.
Let's get started.
REMOVING THE CONTROL KNOBS 1. Remove the control knobs.
a. Pull the control knobs away from the valves.
INSTALLING THE NEW CONTROL KNOBS 2. Install the control knobs.
a. The attachment point for each knob is shaped like the letter D.
b. Verify that the flat portion on the knob aligns with the flat portion on the valve stem.
c. Press each knob into place to secure it.