In the spirit of the excellent post from Intrade, here is a quick easy tip that I use all the time.
If you suspect you have a bad electrical ground, instead of straight away pulling it apart and cleaning it. Grab your multimeter, hook it up in parallel with the suspect earth cable and set it to volts. Then have someone activate the electrical device you are testing.
The reading you see is the voltage drop, or to look at it another way, how much voltage your earth wire is FAILING to transfer back to ground.
Obviously zero voltage or there about's is what you are looking for.
So? Why do this instead of just cleaning the terminals. Well often it's much quicker (access issues) and it also confirms whether this was indeed an issue.
If you liked this tip I am happy to do more from time to time. There is even quite a bit more on this same subject that is very useful to know. If any auto sparkies want to jump in and add more, improve on what I said by all means do. I have tried to keep the language and explanation as simple as possible, you might want to do the same.
Happy motoring.
mechnificent,
Feb 20, 6:31am
Good post Jazz.
I'd add that it's always a good idea to confirm faults BEFORE pulling them apart. whatever they are. If you can't confirm the fault, at least figure out how to cause/induce it repeatedly and predictably so that you can test it to ensure you have cured it after the work is finished.
thejazzpianoma,
Feb 20, 6:36am
A little extra add on to this if you followed up to this point.
If you think about what we are doing here, you will likely realise that this can be used for a lot more than just testing suspect ground wires. For starters, it can be used to check any suspect area of a circuit.
Say you have a car with the old round fuses, they all look intact but your lights are dim or something isn't working. So perhaps those fuse contacts are not so great.
Using this method the fuse is the suspect part of the circuit. So just like we ran the voltmeter in parallel with the earth wire, we can run the voltmeter in parallel with the fuse by putting one probe on each contact of the fuse holder. Fire up the circuit in question and look for a notable voltage.
This method can be super speedy if you have a lot of fuses to check.
If anyone doesn't understand what I am talking about or realise what I mean by "in parallel" speak up, there is no judgement from me.
thejazzpianoma,
Feb 20, 6:40am
Thanks and couldn't agree more! Lots of reasons why this is good, but one that springs to mind is often with this stuff you may improve one part of the circuit that then enables enough voltage for the item to work "just". It's nice to know if there are more weak points that need tending too, and a voltage drop test will tell you straight away. Likewise if something is failing intermittently, it can be so easy to "catch it in the act" when it actually decides to fault with this method. Not always easy to pull things apart on the side of the road!
sr2,
Feb 20, 6:49am
Great thread.
An invaluable skill taught to me by a good friend who was a forensic metallurgist is simply to look with your eyes, not your hands. We all have a tendency to touch and poke at broken or faulty components often destroying crucial evidence we can use to diagnose the fault.
thejazzpianoma,
Feb 20, 7:35am
Thanks sr2, since this seems popular here is another add on, on the subject for those interested.
OK, so you might be reading this and thinking, hang on, I have a resistance/ohm meter function on my multimeter, if I use that I don't have to worry about having someone activate the circuit to get a reading. I can just use it to directly test the suspect area of the circuit. That's what it's for right?
Well. here lies the trap. Many ohmmeters actually use the voltage drop test principle I explained above to calculate the resistance value, that's how they work. The problem is multimeter ohm meters don't apply enough load for most automotive test applications.
Think about it, you wouldn't try to jump start a car with a pair of little speaker wires would you? But if if you put your ohm meter on a good speaker wire you are going to get a "good" (low) resistance reading. The same principle applies, even if the load isn't as massive as a starter motor.
Multimeters apply a tiny load with the intent of measuring electronic components and the like. The best load/resistance for testing a particular circuit is usually the actual load created by the components in the circuit, hence the voltage drop test with the actual components used in the circuit creating the load, works very well.
If this isn't clear enough for you, speak up, and I will be happy to try and explain more clearly.
shall,
Feb 20, 7:52am
Has anyone tried is ? The times I have needed a small load would make this a handy addition to my multimeter
Those can be great for a commercial user, but you do have to bear in mind a couple of things.
1. A test light (old fashioned bulb kind) creates a load and this can be a a great inexpensive alternative and the bulb itself can be a great speedy diagnostic indicator even without the multimeter attached.
2. If you are introducing an artificial load (as opposed to using the components in the circuit to create the load as I have outlined above) you need to be VERY clear and confident in what you are doing. Apply a load to the wrong place on a circuit that involves a connection to an ecm (computer) and you can be in some very expensive hot water.
It's probably worth us having a discussion regarding test lights as a follow on from the above. I find they are often horribly neglected nowadays as people rush for the multimeter. The humble test light can be a fantastic tool for speedy diagnostics. Not only can you use it for load tests and all the obvious circuit testing. It can also act as a "safety" device a bit like a fuse.
Say you want to apply power to something to test it, but are worried it might have a short or that you may accidentally create one ( say it's in a tricky spot and your test probe might hit ground).
If you use a direct connection to a battery with wires in this situation you could be in trouble. However if you use your test light in place of one of the wires, if there is a dead short the bulb will simply light and there will be no expensive fireworks show!
Obviously, still use care, the test lights resistance/protection may not be appropriate for sensitive electronic circuits for example. Likewise you wouldn't go the other way and try to jump start a car with one.
shall,
Feb 20, 8:14am
Yes, understand the problems with it. Just wondering if I may get any value of carrying it with my multimeter. Some of my testing is noth ECM related as not in cars, and most the stuff I test is in addition to the car which would have a current draw in several amps anyway, so should have already been taken from a location that is not ECu sensitive. Don't know I would benefit from it a lot, but times I would have
thejazzpianoma,
Feb 20, 8:20am
If you already have a test light the advantage of the loadpro is only a little extra speed/convenience. I doesn't "do" anything special as such, it's just some leads with a switch and a resistor.
So, if you do lots of load testing, yes it's great. If you only do this sort of testing occasionally, then nah, save the room in your toolbox and your money IMO.
BTW. didn't mean to sound condescending above, was meaning my post to be of use to the general audience rather than just yourself. Hence the lengthy explanation, as the loadpro bought up a great point of discussion.
shall,
Feb 20, 8:22am
Oh don't worry, didn't think it was condescending at all. I see people at work randomly probing wires with a test light all the time. One day they will have a problem by sucking too much from the wrong thing and it's all over in an expensive way ;)
I'm still of the same opinion as you so agree fully, nice and interesting but a luxury to have the loadpro only :)
intrade,
Feb 20, 8:24am
load pro test leads is a petented tool i got them along with dan sullivans book. dan sullivan is the inventer of this tool , he is also the only guy who teaches professional understandable ohms law volt ohms amps , and not e -i R crap that no one can remember.
thejazzpianoma,
Feb 20, 8:25am
Just as another thought. if you are not going to leave the loadpro connected to your multimeter all the time (and you may choose not to, to reduce bulk). Then you have to ask how much extra convenience it adds, if you are then going to do a whole bunch of load tests in a row, then probably still good. Otherwise, a nice (and cheap) selection of different multimeter probes (alligator clips etc) may be almost as useful.
But hey, if you have the money and toolbox space to burn, go for gold!
thejazzpianoma,
Feb 20, 8:30am
LOL, yes gotta be wary of random probers.
You should always understand the circuit you are doing anything too IMO, at least to the degree of understanding what "might" be attached and where so you can take adequate precautions. So I agree with your sentiment entirely!
If excess load is your concern (as opposed to adding a resistance for safety because of risk of shorting) then an led test light can be the go. It's great to have one or several of both. They are cheap as chips nowadays online. But again, you need to understand the circuit to the point of knowing which you want to use to negate the correct associated risk.
shall,
Feb 20, 8:31am
I do have my weekly tool allowance adding up but think it will go in a new battery drill instead. :) it's not often would use load pro and survived without it till now :) sometimes I make sour of the moment decisions and that might be the time I buy one hhaha
intrade,
Feb 20, 8:33am
seriously you want the load pro test leads because pushing that button takes secounds to what it will take you to otherwise test with a extra load conected or making sure you mesure a wire loaded also and this has been told by bosch germany by aecs and by dan sullivan and by any other professional technition ohming out things is a bad idea a ohm meter is not capable to load a wire so it can mesure if its faulty or not. a faulty component can ohm perfectly fine . its why you should never ohm test things when you have a other option of testing.
intrade,
Feb 20, 8:35am
shall wat trade are you in?
thejazzpianoma,
Feb 20, 8:35am
LOL, yes it's one of those things that's likely to be demonstrated really well at some show and you have to have one there and then!
BTW. check out Milwalkee and AEG drills if you haven't already. I have been doing loads of research while I wait for my tool account to fill as I am looking to upgrade my old DeWalt stuff. Different markets those two brands but AEG seem to be really good value as they are the "new guy" in our market. I had the chance to compare their battery's (as in pulled apart ones) and was quite impressed, the Ryobi One battery was a piece of junk under the hood by comparison. I am considering Milwaukee for their excellent impact wrenches in the same range. There is an online NZ Milwaukee importer who was doing some very sharp deals, cheaper than importing yourself in many instances.
shall,
Feb 20, 8:48am
Actually the aeg is what I am looking at, just the allowance isn't quite there. Looked at the makita and dewalt brushless versions for a bit more efficiency but cost too much. The aeg comes with 6 year warranty including 3 on battery which is the deal that will sway me I think :) and to Intrade. I'm a radio technician, mainly on the network side of things , repeater sites etc, but have to check the odd install in a vehicle, find plenty of bad connectors, fuse holders, joins that have been sitting under wet carpet of a van for years, fine with multimeter unloaded, but just can't do the transmit current. Like I said not often I need to load test though
shall,
Feb 20, 8:49am
Oh and who is the online dealer ?
intrade,
Feb 20, 8:58am
if your a radio technition then you want a scope . this guy is why i did buy a 3500$ pico scope and not a 100 one-hang-low model He explaines scopes and tells you why cheap ones are no good and why expensive ones cost what they cost. https://www.youtube.com/channel/UC2DjFE7Xf11URZqWBigcVOQ for radio tech work you need a good scope.
thejazzpianoma,
Feb 20, 9:00am
Haha, I knew you were going to ask that. I think I have it in my endless sea of bookmarks somewhere. Will have a look for you!
Edit. can't seem to find them in my bookmarks. If you want to have a look for them, I stumbled across them in the weirdest way. I was checking out Ebay (at least pretty sure it was ebay and not amazon) for a 1/2" Milwaukee impact wrench, and the cheapest one listed was from NZ. Which is weird because it was about the only time I have seen a NZ listing on there.
So, if you really want to know, you might be able to find them the same way. Otherwise, yell out and I will have a troll through sometime for you.
shall,
Jun 7, 3:05am
I'm weighing up if I even need a scope now, since I am mainly the network side of things, repeaters and infrastructure at sites, it's not often I go past my hp8920 analyser, anything component level now goes back to workshop and fixed by our bench tech, I will only occasionally do it if he's not round. More and more mine is just rf and IP now.
A scope is often handy just to see audio is available to linking radios etc,
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