[Mgs] Overdrive does not work when it is hot. Checking for an open circuit

[Paul Hunt]

It's not me that is missing the point or failing to understand, you don't 
seem to understand when we describe the same thing in different ways e.g. 
additional resistance in series with the circuit and how it can be used. 
But invoking headlights when the issue is with the overdrive is pointless. 
Forgive me for stating the 'bleedin obvious' (as Basil Fawlty would say) but 
you can *see* when a headlight is on normally, dim or off altogether by 
looking at it.  You can't see if the overdrive solenoid has normal, lower 
than normal, or no current at all flowing through it *except by measuring 
the current in the circuit* with an ammeter inserted at one single point. 
If the headlamp filament is broken all your multiple voltage tests along the 
circuit will tell you nothing useful, except that you have 12v at the bulb. 
Ditto the solenoid winding if it is that which is broken.  Until you can see 
that you will get nowhere.  I'm sure everyone else is regarding this 
discussion with either amusement, irritation or the delete key.  I'm also 
sure that you will continue to recommend your way and I will recommend mine, 
the difference being that mine will deliver something useful!  Thank you and 
good night.

PaulH.

----- Original Message ----- 
You are still missing the point.
Let's take a lighting circuit for example as it may be easier to understand