The Glow Plug Relay turns on the glow Plugs for a certain amount of time and then shuts them off so they don't melt. They literally glow inside of your cylinders to help with the cold engine start up. Why are you replacing your glow plugs? Do you have a starting problem?
My mechanic told me that a couple of plugs need to be replaced. So I am going to purchase them online and have a buddy replace them. So I was wondering if I should buy this as well. Thanks so much for your response.