What produces magnetism?

[david58]

Most of the electrical units in a car employ not only electricity but also magnetism which is produced by electricity to make them work. Here is a partial list of electromagnetic units. The starter motor, generator or alternator, ignition coil, horn, horn relay, solenoids, voltage regulator and the list goes on.
Now here is my question. How can magnetism be used to properly diagnose an electrical problem?

[Piledriver]

Easy if it's an AC circuit...

Much harder if it's DC, and impossible if theres no actual current in the circuit, as there won't be a mag field.

So to answer your question... Not really useful except to check of a relay is getting juice to the coil etc.

An idiot light is far more useful in the right hands.

[nsracing]

Easy if it's an AC circuit...

Much harder if it's DC, and impossible if theres no actual current in the circuit, as there won't be a mag field.

So to answer your question... Not really useful except to check of a relay is getting juice to the coil etc.

An idiot light is far more useful in the right hands.

What kind of crock is this?

Does someone need a lesson in electricity? YOu can grab a basic principle of electricity and read on it.

Magnetism can be produced by electricity through induction or by permanent magnets. Either you use the magnets (permanent magnets) to make electricity (generator)...or use electricity to make magnetic fields and induce electricity (alternator). This is not hard to understand if you know the principles of induction.

One thing I will recommend is to learn each piece of equipment on how it uses electricity..or magnets...or both to accomplish something.

Relay...all it is something that controls LARGE voltages with small voltages. It is a freaking switch! YOu can get them normally closed or open.

Coil... all it is a large capacitor...or "UP" transformer really. It uses induction principles using small voltages and creating large voltages (secondary voltages).

I will say that to understand electricity....one needs to learn the relationships of Voltage...AMPerage...Resistance. All it really is MOVEMENT OF ELECTRONS.

A test light is a simple tool used in diagnosing a lot of the electrical things in the car. But you also need to learn to use a Volt/Ohm meter. These two pieces of equipment should be all you need to diagnose electrical problems.

Besides...there are NOT that many electrical systems in the car anyway.
Charging system...lighting sytem..starting system...ignition system. These are not hard sytems to learn.

HOpe this helps. I would love to type more but my fingers have arthritis.

[Piledriver]

NSRACING--

I answered the question as asked, correctly.

Question was:
"can I use magnetism to troubleshoot..."

Check my profile.

[nsracing]

I was not sure how to answer it. But if you think you have given him the right information is fine.

There are magnetic pick up ammeters than will tell you if you have current in the line WITHOUT breaking the line. Get them from HOME DEPOT. YOu just clamp on and read.

But a simple test light is better.

[Piledriver]

Clamp on ammeters require an AC signal... No workee for DC.
Great for your house/factory etc where you have AC power for everything. I use them all the time.

For your car, not so much...

The "clamp" contains a transformer coil of sorts... very much like an inductive pickup on a timing light.

Doesn't work without a changing signal AND some current, either pulses or AC.

They make neat little troubleshooting devices that "light up" an LED (might be a tiny neon bulb) or such when held near a powered solenoid or such, just hold it near it. Only works on AC tho, for the same reason.
Requires no batteries... just has half a tiny transformer in it, and the coil in the solenoid makes the other half... but it must have current passing through the solenoid to work. I have a couple rattling around in my toolbox.

[Marc]

There are indeed inductive-pickup ammeters which work quite well on DC. Without them, electrical-system testers like the Snap-On VAT-40 couldn't function. There are even small hand-held meters that give a reading when positioned alongside a wire of the circuit under test.

http://en.wikipedia.org/wiki/Clamp_meter

[Piledriver]

Cool, I stand corrected, but I rather doubt they sell those at Home Depot.

I'll have to order one for my Fluke meter...

(Been ~25 years since I was in school. Nice to learn something new)

[david58]

The reason I brought this up is because I have seen over the years mechanics use a screw driver or wrench to see if an alternator had a magnetic pull while running and if it did they would say it was charging. I don't know if it was true or not I never checked behind anyone. I was told if the shaft was magnetized it was charging.

[Piledriver]

I believe that would be more of a test if the mechanic owned a working voltmeter...

You could easily have a alt with some bad diodes that is still producing some power that might pass that test, but not keep up with normal load.

As long as you know it's limits, a test light is all you usually need for troubleshooting.

Even a DVM has its limits, as it is a high impedence device, it can read "correct" voltage in an open circuit that may be coming through a high resistance (corrosion etc) ... and could never flow any significant current.

[david58]

I believe that would be more of a test if the mechanic owned a working voltmeter...

You could easily have a alt with some bad diodes that is still producing some power that might pass that test, but not keep up with normal load.

As long as you know it's limits, a test light is all you usually need for troubleshooting.

Even a DVM has its limits, as it is a high impedence device, it can read "correct" voltage in an open circuit that may be coming through a high resistance (corrosion etc) ... and could never flow any significant current.

How about explaining how to read amps with a test light.

[Piledriver]

I don't recall mentioning that it could...

Tools all have their limitations, but if the light doesn't dim out when you turn load a circuit , you probably have a good connection, and no shorts. (/me shrugs, all I have )

Most people should learn how to use one, first.
It is handy even if you have a meter. It has its uses.

Most electrical troubleshooting on a car will be of the go/no-go sort. For anything more , a multimeter is required.

Just be aware it can lead you astray as well.

Detecting some current by magnetism with a screwdriver gives you an INDICATION of something. It does not give you a measurement, other than your alt/starter solenoid/coil isn't completely open, and some power is there. I suppose it also indicated you don't have a SS screwdriver... but that's about it.

If that's all you need to know, good for you.

The alt could be maxed out and supplying 10v into a dying battery with shorted cells, of have a toasted reg and about to blow your battery up from overcharging. It could have some shorted diodes and be sinking that current internally.

The starter solenoid could be getting SOME current, but not enough to pull in, or it could be gunked up... No way to tell which, and a frequent scenario.
A bright vs dim test lamp will tell you if it's getting sufficient voltage so it SHOULD pull in...

Detecting the field against the case doesn't tell you enough to call it troubleshooting. Maybe in desperation.
If all you HAVE is a wrench... It beats licking the connectors. Sparks tell you something too...

[fusername]

clamp meter, had no idea you could do DC. If anyone knows what one of those runs, they could be nifty!

piledriver, did you just try to use /me?
other than that, well put.

doesn't tell you enough to call it troubleshooting. Maybe in desperation.
If all you HAVE is a wrench... It beats licking the connectors. Sparks tell you something too...

I think that sums it up. Sure, it tells you SOMETHING, but it does not say good/bad. it just says one of several components of the item are working. I'm a fan of numbers and schematics and lists of things to trouble shoot.

....what was the topic again?