I notice that in the gauge cluster of my '75 Maverick there is a light that says "Low fuel Econ". I received this Mav far from stock, how did this originally function? Was it hooked up to vacuum with a switch, so when the engine was pulling lower vacuum (more throttle) it would light up?
My 77 had that light, but it did not have anything hooked-up to it. I don't even think there was a bulb behind it IIRC.
can't say that I know exactly what you're talking about here.. but the functionality of such devices would have to be and typically are based off of the engines manifold vacuum since that's a direct measure of an engines load and efficiency for any given throttle angle. Less throttle angle with lighter load will always equate to more engine vacuum on a decently tuned and sound running engine to give greater efficiency.
Interesting, mine will light up when cranking, but never comes on again. I will try to post a picture later. I may repurpose it