<VV> Late model headlight switch - problem solved

[David B. Neale]

"Past experience tells me that a better tool is a circuit tester which has a light bulb.  In cars that have been around for a long time it is possible to have enough dust / dirt collected on the fuse to leak voltage and show as a working circuit even though there is less than enough amperage to energize the circuit!   
Ken P"


You are essentially correct, Ken; especially with a modern meter, which will draw so little current almost any circuit path around and through an open-circuit, (blown), will register, possibly,  full battery voltage on the load side of the fuse.b This is where, if a meter must be used, an old-fashioned, low-resistance, (read cheap), meter will give best results.

It would make sense when measuring with a meter  to have any device that was fed through the fuse switched on. so that the load's attempt to draw power would indeed cause any meter to read zero in the case of measuring on the load side of a blown fuse.

And yes, a bulb is much, much better than a meter for the job; and a buzzer, too, for those times when you are upside down in the car, head wedged underneath the dashboard, eyes having diifficulty focusing, and unable to monitor a bulb, let alone a meter.

David

'65 Monza 140 4-speed convertible in  leafy Leicestershire, heart of a wet, cold Autumnal England