The V8 Owners Forum -

having an electrical nightmare the now so i'm having to start working my way through testing connections, so ive treated myself to a multi meter i know how to check a battery thats it, hopefully getting to grips with electrics now, what do i put the dial at to check if there is currant going through the wire connection and parts i,e pumps solonoids coil etc:, i feel like a dumbass here asking this as i thought a few peaple i know knew how to work these, cheers, nimmo.

I know how to use one.
But it's a bit like thinking that because you've got a set of spanners, you can rebuild an engine.
Try this for starters:
http://www.doctronics.co.uk/meter.htm

Chris.

cheers chris, spot on mate.

If you struggle with electrics, I can recommend a Haynes book - Automotive Electrical and Electronic Systems.

It explains the basics in a pretty easy to understand way - as well as being a wealth of information for the more experienced too.

As regards using a multimeter, one of the best ways in practice requires some lateral thinking. Just unplugging something that doesn't work and measuring that there are volts getting to it tells you little. What you need to do is measure things with it plugged in and drawing current. And since many problems are caused by poor connections somewhere in the circuit feeding it, a good way is to measure the voltage drop in the entire circuit.

So say you had a headlight which was a bit dim.
With the headlight on, measure the voltage from the battery positive to the bulb centre contact. Wisdom would say this will be zero - but in practice the wire, switch, connectors etc all have a resistance so it will read a small voltage. If the circuit is good, it will read less than 0.5v or so.
If there is a problem, it could read several volts. Do the same from the battery earth to the bulb body.

This is a quick and accurate way of finding problems.

Wot Chris and Dave sed!!
A digital AVOmeter (AmpsVoltsOhms) is notoriously "inaccurate" in inexperienced hands.

unstable load wrote:Wot Chris and Dave sed!!
A digital AVOmeter (AmpsVoltsOhms) is notoriously "inaccurate" in inexperienced hands.

Yes. Just to explain, the meter itself draws effectively no current from the circuit it is measuring, unlike a mechanical (needle) meter. This is a good thing when measuring very low current circuits, but has disadvantages too.

For example when checking mains on house wiring, you might find it reads 240v on a wire which isn't connected to anything, but is close to ones which are. This would worry someone who doesn't understand why

Hence the rule always to measure the circuit under load. Which is more difficult to do in many circumstances.

nimmo wrote: hopefully getting to grips with electrics now, what do i put the dial at to check if there is currant going through the wire connection and parts i,e pumps solonoids coil etc:, i feel like a dumbass here asking this

Nimmo, the former tech guru of the Rover SD1 Club put together a helpful document for using a multi-meter on cars.

You can read/download the PDF from here:

http://www.vintagemodelairplane.com/pag ... ter01.html

there are also some videos available on the link page, so you will soon be an expert!