Hello, John Talley here with Partzilla.com, and I know whenever the
subject of electricity comes up everybody gets really nervous. Well
shouldn't be that scary of a topic to cover, but one of the most asked questions
is, well, what I really need to dig into the system? Something as simple as just a
test light or do you need to step up and get what they call a multimeter? That's
what we're gonna talk about right now. A test light is a very useful device--
inexpensive, it's really easy to use. But basically all it's telling you is if
there's electricity present there. And that may be all that you're looking for,
but in most cases you need to know how much. You need to know the measurement of
the voltage or amperage or resistance and that's something that it simply
can't do. And what the test light is very proficient at is giving you a quick look
inside to see if you've got voltages and or if something is ground out depending
on how you connect it. Yeah, a simple voltage test to see if there's any
electricity present. Put that on the negative side, go to your positive, lights
up. But it doesn't tell you how much voltage is actually present. That's where
the digital voltmeter comes in. Now there's another neat way you can use a
test light. If you're trying to trace down a ground somewhere on your system,
simply move the clamp over to the positive side of the battery because it
doesn't care about polarity. Now you can start picking apart that wire and find
your ground. Now one thing I want to caution you about if you're trying to
trace out a bad wire or a grounded out wire on your fuel injection system, you
have to be very careful when using a test light. Because most every single
fuel injection system I know out there is controlled by your ECU. And what you
basically have here as a pathway to ground. And the grounds don't play very
well when you're talking about an ECU. You can fry one in a hurry-- not that I've
ever done it, but I've heard that it happens. So you've made the decision, all
right I need a DMM or a digital multimeter. Which one do I need to go
with? Well, if you've watched any of my electrical diagnostic videos, I always like
using the Fluke unit. Really high quality, and very accurate. But that doesn't mean
you have to spend the money to get something this nice. For as little as $30
you can go with this little Lang unit that'll do all the basic requirements
that the Fluke will do. It'll do resistance, voltage, AC and DC, it'll do
a diode test. It will also do an amperage test, and providing of course that you
don't exceed its internal fuse which I believe is 10 amps. One of the biggest
difference in between these two units is the Fluke is actually automatic. When you
switch it over to voltage, AC or DC, it automatically scales it to whatever the
input happens to be. That's one of the disadvantages with the cheaper unit: it
actually requires you to pick the range. So, just as an example, if you were going
to do a battery voltage measurement on it, you'd want to put it in the 20 volts
DC range. That gives it a range from zero all the way up to plus 20 volts. Let's
see how much voltage this battery does have just for fun. Twelve point four zero.
Just for kicks, let's turn on our Fluke. DC. 12 point four four. Which one do you
believe? I'd probably edge more toward the the Fluke, but once again, 0.3 of a
volt difference-- actually 0.03. So that much of a different-- that small of a
difference-- you're safe to go with the with the Lang instead of the Fluke
Let's do a quick test of the diodes and compare the two meters. So we've got our
in diode mode and let's see what all kind of readings we get. Should be around
point five one.
And flip on our Fluke take it over to diode. Four-nine-nine. Four-nine-nine. or yeah, four-nine-nine.
Is it a little off compared to the Fluke? Well, maybe just a tick, but that'll still
tell you that the diodes are working in this particular unit. Now if you do need
to help really diagnosing and looking into the inner workings of a regulator
rectifier, we have a video for that you may want to go check out where I take a
relatively deep dive into what you can and can't see inside of one of these
devices. So you've made the commitment to go ahead and diagnose whatever
electrical problem you may be having. So which one do you need? Well in my opinion
go ahead and get both. The test light just for quick and dirty when you're
trying to see if there's voltage there or not, but being very mindful which
circuits you're messing with because we don't want to damage the ECU. I'm gonna
stress that. The multimeter is as its name implies. It has multitude of uses
and they are actually so inexpensive right now why would you not want that
type of capability? So go ahead and put both of them in your toolbox. For a very
small investment you open up a large window when it comes to being able to
look inside and diagnose your own machine. If you have any questions or
comments, leave them in the section below and I'll do my best to answer them. If you
need a little help diagnosing your machine, check out our playlists. In every
unit, we at least do one or two videos that deal with diagnosing electrical
problems. If you have a specific question about a part or tool give us a call or
send us a message and we can get the answer for you. Listen we just want to
say thank you for shopping here with us at Partzilla.com and we will see you in the next video.