Glow Plug Light

[Ol'Smokey]

Hey guys, new to the forum. I am the proud new owner of an 81' 240d. It is in really nice shape and has 163,000 miles on it. So far I love it to death. It is not my first diesel, but it is my first Mercedes diesel. My question is about the glow plug light on the dash, it doesn't come on. The plugs and wires are new within the last year. The car came with two controllers. The one he had in the car was apparently supposed to stay on for 30 seconds after the car started to help it clear the smoke faster, and he also had a "stock" controller. Shortly after I bought the car the light stopped coming on. I thought the controller went bad so I just changed it out today with the other one. Light still doesn't come on. I checked the fuse box and there was one bad fuse (c). I noticed there is some kind of temperature sensor thing that looks like it is tied in with the glow plug system. Could that be causing the problem. Thanks for any advice.