I posted some voltmeter photos in another thread last night. The photos show that the voltmeter does not show a drop in battery voltage when the engine is not running. This is a design defect, because another member reported the same thing. With my 1999 Ranger, the voltmeter showed a lower reading when the engine wasn't running as expected. For many years, Ford has used a "idiot light" type of oil pressure gauge that shows either no oil pressure, or around 1/2 scale when there is oil pressure. This is due to a normally open switch for an oil pressure sending unit, not an analog type of sending unit that changes resistance with a change in oil pressure.

For a comparison in voltmeters, I checked my son's '12 Tundra, and it is designed correct, and shows a change in battery voltage:



'05 F-150







'12 Tundra

 

An update: I went to the Ford dealer and looked at the '12 F-150, and F-250. They have replaced the voltmeter with a tranny temp gauge. The dealer had a '07 F-150, that did have a voltmeter. I checked it, and the voltmeter is working as it should:



’07 F-150

 

Does anybody have access to a Chevy to try this experiment on?