I have a 1979 Ford Chateau Superwagon E-350. I figured I'd ask her since not many posts in the econoline thread.
The intrument panel looks the same as the ones in 1970's Ford Trucks so I am sure someone here will know.

The temperature gauge is not working. Any clue where I can start to repair this?
My brother said its a vacuum line going to the a box somewhere. I have no clue and he will not take the time out to show me.

I need to repair the radiator in this van and its important to me that the temp gauge work properly. Thanks for reading!