Brand New Heavy Duty Automatic Glow Plug Controller for all 96-98 H1 Hummers. Make sure your relay/controller has 3 pins on the connector as shown.

This controller is what turns your glow plugs on and off by a signal from the computer. Replace when glow plugs are not operating properly or when DTC codes indicate controller failure. I recommend replacing every time to plugs are replaced as preventative maintenance or every 100K miles.