I am a bit puzzled. I have a 94 E350 van, 7.3 L N/A, glow plug controller at the rear of the engine, easily accessible via removal of the dog house in the cab.
I flat do not trust that relay. It is claimed to have aluminum contacts. I have had nothing but disaster follow every time I have ever mixed amperes with aluminum.
Something to do with deformation of the aluminum, oxide formation, subsequent resistance, followed by current induced heat, followed by an inevitable thermal destruction. Spitzen mit Sparken. With fire.
I bought some industrial White Rodgers contactors to replace it, but it's not an exact mechanical fit.
https://www.amazon.com/RODGERS-586-902-CONTACTOR-SPST-NO-BRACKET/dp/B00DE3HY4K
Is there some surprise lurking for me beneath the existing controller?
Was it a glow plug, or something in that controller ( engine temp sensor ?) that broke off?
I want to pull the whole controller assembly, and replace it with that White Rodgers contactor and a pushbutton.
Later maybe I'll have an Arduino output pin do it, but button for now.
I often don't need to cycle the glow plugs at all. And I want to clean that area out so I can install a homebrew current monitor to make me aware of plugs that aren't taking their proper current.