On 08/05/18 18:07, Graeme wrote:
In message , Adrian Brentnall
writes

Just a thought....
If you have a voltmeter of some sort - connect it across the 12v mes
bulb in the above setup.
Naturally, there'll be a voltage drop across the bulb when the door is
opened, but is there any volt-drop across the bulb when the door is
closed..?Â* If there is, that indicates that there's a small current
'leaking' through the interior light, via the door-switch.

OK, good idea.Â* My multimeter is an ancient Eagle analogue, which is
great for current is/is not there, but difficult to detect minor (ha!)
variations, particularly as the closest scale is 0-50v.Â* I'll have a go,
though.

Car batteries are designed to provide lots of current for a short
period of time, to start the engine. They're not good at long-term
supply of smallish currents... - and the car ammeter won't indicate
accurately down at that level...

I know you're right.Â* I'm sure I have an analogue 5amp meter somewhere,
but even that will probably not detect a small drain.Â* Will try anyway.

Come to that - can you put a test meter across the in-car ammeter?
With everything off there should be no voltage. A sensitive voltmeter
will tell you if there's a small current being drawn from the battery,
even when everything on the car is 'officially' off..

Say that again.Â* Assume I have the ammeter (which is not fitted in the
car) between the battery -ve terminal, and the earth lead.Â* Where do I
connect the volt meter?

across the ammeter.

But better to get som small load like a bulb and connect that in series
with te battery and look at the volts across that esp. if you can go
down to mv

In fact, just connect a 12v meter in series with the battery. There
should be no drain whatsoever.





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