Flat Rate Mechanic here and today we're gonna go over how to test any relay and
In this video, I'm gonna be showing you a relay testing hack you can
do inside your car we're gonna be testing the relay using
a battery how to test a relay using a test light how to test a relay using
power probe and how to test different style relays you have your 3 pin relay
4 pin 5 pin relay and so on so and I'm also going to be actually putting a relay
to use here as you can see I have had this metal halide light bulbs sitting
around so I figured it'd be cool for that to use so you can see the ballast
sitting over here so let's just go ahead start by explaining why they use relays in cars
the main purpose for using a relay is to basically control a high amperage
circuit with a low amperage switch the reason they do that is basically when
you got when you're powering if you're powering a high amperage circuit with a
switch every time you hit that switch there's gonna be and eventually what
that's gonna do is we're on the switch just like just like on this power probe
I have here when I hit the switch this obviously doesn't have any type of relay
circuit so if I'm activating a high amperage circuit with this say like I'm
going to power up a fuel pump with this rather than hit E or rather or say I'm
gonna power up a starter with it rather than putting this on the starter then
hitting the switch I would probably put this on the start at first or hit my
switch first I'm fit on the starter so the arc happens here rather than inside
the switch so that's one of the reasons why they use relays as if you were using
a relay if you're activating a high current circuit with the switch sets
which is gonna wear out very quickly you're gonna melt the switch up so also
it saves a lot of wires because we can activate this we can act
is relay with small watch small gauge wiring like this whereas the hi circuit
portion of it via via fan motor or AC clutch or someone of that nature we
reduced the amount of height gauge large gauge wire we need so let's go ahead and
I'll show you guys how this thing works here first off just so you guys can see
now this one I'll also show you guys real quick how you can tell which pin is
which as you can see this one didn't have any labeling on it so by looking at
it and a lot of times I'll even have the leaving up numbers right here and you
can see here this relay doesn't have any so there's really no way of knowing
which one is which oh actually I guess it does have numbers well you know I can
see it in the screen because it's magnified but I actually couldn't see
that with my bare eyes but yeah you can see the numbers there you got an 85 30
and so on and if the cover was still on the relay this it would probably a diagram but
there isn't I'll see if I can find one and
pop a screen shot up with that but alright so basically what we have inside
this relay coil is we have a switch which is here this is gonna be the high amperage
side and a lower amp side all we have is a magnetic coil so
what this really does is we're powering up this magnetic coil with a lower
amperage to activate this switch in the relay and as you can see here so once we
apply power to the circuit via the switch here it's
going to just going to magnetize our coil and it's gonna pull this relay switch
close but in high amperage current flow through here so in order to find out
which relay legs we need to test without diagram
we're basically going to check resistance between these terminals and
we're gonna have we're gonna find we're gonna have continuity through the coil
side and no continuity through the switch side so I'll go ahead and do that
I'm gonna set my own meter to ohms here which will be down there and oh I'll
just means open you see they're showing 1 ohm zero ohm so that's what we
want and then we'll test use to see which one is open
all right so we got resistance there so I'd say that's our coil side you see
these on this one is the other actually across from each other and here is open
time so looks like these two pins these two pins here are our coil side
nobody'll yeah so what I have is I actually have these two test leads hooked
up to a battery so we can test this relay it that way just with power and ground and the
polarity doesn't matter all it is a magnetic coil so
our probe here actually and this power probe I have that's basically doing the
same exact thing those two leads are so just hook to the battery and gives you a
power and ground circuit so
and sell the beeping off here all right so we can hear that relay clicking see if we
can get a good shot of that
there we go if you guys can see that relay activating so we're energizing the
coil and it's closing the switch for the higher amperage circuit so let's fire we
know we know the coil is energizing so what we're going to want to do next is
let me actually hook this test leads up so I can power this relay continuously
how to test a relay
all right you guys can hear that clicking we got it activated there and
now I'm going to check continuity through the high current side or the
switch side I guess we would call it on this relay
all right now as you can see there we have continuity so this relay is testing
good now another step you may want to you may want to go one step further here
because if it worked or I buy ground to the to the high current side so we're
gonna treat we're going to treat this high current side as if it's powering
this light bulb so I'm just gonna do this to make sure that this relay can
carry a load so as you can see there it can carry a load so this is definitely a
good relay basically when you're testing a relay with a meter it's telling you
that there's continuity and the switch is closing in the relay but it's not necessarily
telling you that it can carry a load because when you put electrical circuit
under load if there's any if there's any high resistance or problems in that
circuit it's not necessarily going to carry the current and when you have too
much current on a small circuit I'll show you guys what will happen as an
example of this right here which is just a piece of solder but this is not I'm
basically shorting it out through the battery and this is not
- and as you can see it just melted that to solder instantly so that's just a
quick little example of what high resistance can do through a circuit
that's not capable handling it and I just shorted it out completely
now when you testing different size relays if some relays have four pins
some relays have three pins some relays have five pins for instance here like in
this diagram I have a wire for 4 pin but as I actually had 5 pins which would be
an 87 a here all that is doing is putting another leg on the ground on the
open side of the switch so you can actually control 2 components with the
same relay depending on if the switch is open or if the switch is closed so when
the switch is open and beep out it'd be supplying power through 87a when it's
closed it'd be supplying power through 87 so you test it the same way you just
have to you would have to test these two individually and then you would have
there's some 3 pin relays and the three pin really just does away with the extra
power which it just has a power coming in which supplies the coil and when the
coil is grounded it's going to activate the switch over here and then power can
run through to a light or whatever or whatever on you may be powering here so
now I also wanted to show you a testing and how things we do here I'm gonna go
ahead and I'm gonna hook this I got this relay hooked up to this light here we're
gonna see if we can activate that but I have this little relay I just use as a
test relay and you can actually all I did is take a piece of wire I've
stripped it back and then round the wires together and as you can see I
actually twisted the wire around the all the pins this is actually a really good
way to test relays and the circuit because you can make sure it's getting
power ground and it's activating the control circuit by testing it so you
just plug this in you check your powers on your rounds
you can activate the relay and vehicle and then you can test to make sure
you're getting power out and that's going to tell you real quick if all your
circuitry is good and if the vehicle is actually power enough to relay so this
is a cool little hack just rip some regular wire back to us wires on put
some tape around it plug it in works a great quick easy quick easy way this has
two relays and check the circuit in the vehicle at the same time let me go ahead
and see basically what I have here is I've just put the switch side of the
relay in line with this metal halide light and now I'm just going to activate
it with my jumper number wire here that I have up to a 12 volt battery
as you can see that's what annoying buzzing in the background is that's
actually the the transformer or the ballast for this metal highlight I
actually picked this up at yard so I thought it'd be cool to cool to be you
isn't using a video but I think that just about covers it hopefully if you
guys can think of anything else just leave it in the comment section below
also I will leave links to everything I used in the comment section I picked up
this voltmeter super super cheap I think it was less than 15 bucks a power probe
I use this on a lot of things very handy tool there's just a circuit tester that
you hook to the battery test powers and ground you can apply power to it but
I'll leave that a link to that as well so if this video is helpful be sure to
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thanks for watching guys for watching how to test a relay