Not sure what connects here

So I am going through the engine and everything(Coolant, belts, oil, GPs, ...) else trying to get my M1008 road worthy and I noticed on the back of the driver's side engine that there was a connection that looks like it had a vacuum line or breather hose attached to it. I can't figure out what it is suppose to be connected to. The truck fires right up and seems to run fine.
Can you guys tell what it is from the pictures? I tried looking in the TMs and on SS but didn't have any luck. Sorry I still a rookie with these trucks.

That is the Temp sensor for the glow plug controller.
The wire has a different connector end to plug into it.

You must have a manual push button glow plug switch someone added?
Otherwise you I don't think you would have a operational GP system.
Tom

TGP (IL) said:

That is the Temp sensor for the glow plug controller.
The wire has a different connector end to plug into it.
You must have a manual push button glow plug switch someone added?
Otherwise you I don't think you would have a operational GP system.
Tom

Click to expand...

Thanks TGP. That makes sense. Yeah the person before me really jacked up the GP system and remove the GP controller card so I put in a manual switch to make it operational again.

The system still works with the sensor unplugged. It will just glow/wait every time. Even when it is at operating temp. I had a guy stop by after driving from 2 states away and when he went to leave I noticed he had a wait light. he said it was always like that and thought it was normal. He popped the hood and sure enough the sensor was unhooked and the plug was brittle. He let me know he updated it to the newer sensor with the better plug. Good Luck.

Thanks for the help guys!