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00:08
1997 Mazda Miata with a 1.6 liter engine
and what we're going to be doing today
guys is a charging system test this
vehicle was brought in with a dead
battery customer what complaint was he
was driving in to work and some of the
interior components stopped working the
radio shut off and I believe he said his
dash lights quit working as well and
then the car died and would not restart
another symptom he had mentioned to me
was a few days ago his tachometer quit
00:42
working not sure if that's related or
not yet so what I want to walk you guys
through is some charging system tests so
what I like to do before attacking a
charging system is I like to look at a
wiring diagram there's just so many
different designs out there and I need
to know what I'm dealing with I need to
know if it's computer controlled or not
and so I pulled up the diagram for you
guys and what we're looking at here's
your alternator right here you see it's
grounded on the housing we have a solid
01:14
white wire that's going to a main fuse
and then that's coming directly to the
battery so that's going to be your heavy
cable going to the starter that's hot
all the time and then we have another
wire it's white with a green that's
coming from the main relay that one's
going to be hot and run if it's from the
main relay and then we have another one
that's the bulb circuit for this
alternator so when we do our text we're
going to start with the heavy gauge
white wire with the car running and then
we'll move down the line and then we'll
01:46
talk about the results of each one all
right here's a shot of our alternator
sitting in this location down here and
what we can see in the camera right here
this is our B 80 post that's the heavy
cable that comes to the alternator and
behind this hose there's a two pin
connector down here hopefully this will
show up it's right below B it's right in
this area here and I'll get you another
shot on that when I'm doing testing on
02:18
that but for now
we're going to look at the voltage level
on the B 80 post of the alternator my
hookups yellow lead is going to the B 80
post that B my voltmeter positive lead
my negative lead for this I am going to
the valve cover the battery is in the
trunk on this car ideally I'd want to go
to battery negative but I can't for this
test at least not easily and we're
looking at a voltage reading right now
02:50
of twelve point five eight and I've had
this battery charger on here for a while
so this battery should be at least
halfway decently charged I don't like
this test this isn't good enough I want
to start this car and see what kind of
voltage we have on this post so I'm
gonna go ahead and do that you guys can
watch the bulb ear
okay what we normally do is is we check
this at the battery first and I skipped
that part batteries in the trunk I'll
take you back there next you see we have
twelve point one to twelve point one one
volts on this system right at the BAC
03:38
post what that means to me is this
thing's not charging and what we want to
do first is make sure we don't have a
voltage drop between the battery and
here you know really it's not necessary
when you have that kind of voltage
that's pretty good but let's check it
anyway it's procedures that are
important here so to know what my
voltage drop is I have to take another
measurement at least that's one way to
do it and subtract the two and then I'll
show you the actual power to power
voltage drop test so remember that it's
number 12.1 one up here let's go back to
04:09
the battery okay for my lead connections
back here at the battery I have my black
where you going to battery negative and
my yellow lead scope positive going to
battery positive you see at the battery
we have 12.1 6 volts so that means we
have a point zero five 50 millivolt drop
on this circuit roughly between the
battery and the v80 post what that tells
us is this positive cable going to the
alternator is fine now there's another
04:41
way to do this and it would be important
to know how to do this when you have
changing voltages on the system
especially in light of a weak battery if
this voltage was dropping rapidly while
you were doing your tests then it's kind
of hard to calculate that voltage drop
unless you're monitoring the circuit
directly so to do a proper voltage drop
test what we're going to do is we're
going to leave one lead on battery
positive and then we're going to compare
our voltage to the B 80 t-post of the
05:11
alternator and I'll get you a shot up
front of that just know that I'm going
to leave one lead on battery positive
back here for this next test and I'm
going to have to use a jumper wire to do
it because of the length we have here
between the two
so I'm using a jumper wire for this
because my leaves aren't long enough and
I'm going to compare this side battery
positive to the B 80 post of the
alternator see my jumper wire connected
here let's go up front
here's the other end of my jumper wire
05:42
being very careful this doesn't touch
anything metal
this is plastics that this is sitting
over top of so we're fine here my yellow
leaves connected to this polarity
doesn't really matter here guys you can
put your black lead here in your yellow
lead on the dat post of the alternator
or to say that differently you can use
your volt meter positive or negative
here positive or negative up at the v80
post it does not matter it's kind of
tough to see to see my black lead is
down there on that v80 post and then you
06:13
guys probably saw the voltmeter already
we have a point oh six of a volt drop on
this circuit and so again I wish I would
have shown this when the battery was
weak before when we initially tested the
alternator the system voltage was
dropping rapidly while we were doing our
test because the battery didn't have a
good charge and the runtime involved
with causing voltage drops and so when
you do your measurement in the back and
you measure it upfront and you subtract
06:48
the tube for your drop you really
weren't getting a true drop reading we
were getting maybe one to two volt
difference saying we had a two volt drop
in the circuit but system voltage was
dropping and so this test was needed in
that scenario so you know what the
proper voltage drop is on that circuit
this is a power to power voltage drop
test and I know it's kind of strange for
some of you but what you need to
remember is a voltmeter reads difference
in potential and so the difference in
07:19
potential between my BAC post and my
battery post is 0.06 for 60 millivolts
nothing wrong with that at all it
wouldn't matter if this read minus 0.06
that would just be with your leads
reversed and as far as a number you guys
probably going to want to know a number
truthfully you really don't want much
difference between these two especially
on a heavy v 80 post maybe a maybe a few
hundred millivolts at most in particular
when the system is actually charging so
nothing wrong with our BAC posts cable
07:51
to this alternator we need to move on to
these other wires now
alright kind of tough to get this shot
but I'm on the 2-pin connector now on
the alternator and the wire that I'm on
is wait with the green wire that comes
from the main relay and my scope
positive or voltmeter positive going to
that wire and my voltmeter negative back
to my intake manifold or my valve cover
and there's my voltage reading eleven
08:21
point nine six the voltage drop on that
circuit again we would subtract source
voltage but this thing's not charging to
the source voltage has probably dropped
and if you wanted to get a voltage drop
measurement I still have my jumper
connected here we can do that I'm on
battery positive and all I'm going to do
is take this lead off here and this
isn't really necessary I'm just showing
you procedures
the drop on that circuit is 0.08 so of
08:53
course that they're just going to have a
little bit more of a job because you're
going from the battery into the car into
the main relay from the main relay back
out to here there's a lot more wire
there's more components involved so
eighty millivolts on that circuit not a
problem to clean one less generally do
these with an alternator I just want to
make sure I have near battery voltage on
one of those small gauge wires I think
as a rule I think what I normally follow
09:22
is that I want to see a main power that
heavy b8e cable that equals battery
voltage and then I want to see at least
one more wire go into this alternator
that reads battery voltage we can call
it a control circuit if you want to now
we got one more circuit we need to check
and that is this bulb circuit so I'm
gonna move my leads now let's get to
sorry
here's a better shot of our to pin
connecter and I'm now on the top wire
which is the bulb circuit and we'll get
09:55
a voltage reading on that now by the way
that wire is white with a black tracer
this is the one going through the bulb
circuit and the - and you see I've low
voltage on this circuit point zero - and
the thing about that is I'm not sure
what I should have on this I know that
the bulb is ground side controlled if
you want to call it that by the
alternator let's go back to the diagram
we'll talk about all right as far as the
bulb circuit this is where we're
measuring this right here we're reading
0.02 of a volt and we're not sure what
10:27
this circuit should be we know that this
is the ground side of the bulb circuit
and at certain points in time we're
going to have 12 volts here because we
don't want to have this light lit and at
other times the voltage is going to be
low to make that light light and the
thing about this that's missing really
in this picture too is the voltage
regulator which is all internal to this
this is the entire a alternator system
diagram there's no computer involved
there's no field circuit control by a
10:59
computer it's all done internally and
what you guys need to understand about
these is sometimes the bulb circuit is
needed to wake up if you want to call it
that
to wake up this alternator and have it
start charging and so my suspicions here
or that we potentially have a bulb
circuit problem so what I'm going to do
first is I'm going to give you a voltage
measurement here with the key on and the
engine off I just showed you one with it
running we're at 0.02 let's get you back
11:32
to the car and check that with the
engine off I would think at some point
in time I should have high voltage here
if this bulb circuit is functional
another thing that I've had good success
doing with these is substitute what the
bulb would do and so if we think we have
a bulb circuit if we have a cluster
problem or if we have a fuse problem up
here we could take a test light right
here and go to back
battery positive which is really
12:03
essentially what this bulbs doing we're
going to positive when we touch it on
there
if this alternator starts to charge then
we know our problem is over here on this
side of the circuit so that's what we're
going to do I'll give you the voltage
measurement there first and then I'll
show you the test light test all right
there's your Keyon voltage reading on
that wire you see no change here at all
and I'm telling you guys from my
experience from engine running to engine
off you're going to see a difference on
this circuit any bulb circuit that goes
12:33
to the alternator I'll start back up
again let you watch it
so they're going to change point oh two
of a volt
all right so what I'm gonna do now
get you a shot down here she's going to
take my test light the battery positive
touch on that same circuit all right so
here's my setup I have my test light
going to battery positive using my
jumper that was in the back now you can
use the BAC post if you want it was just
interfering with my camera and when I
13:15
touch ground this tesselation light as
you can see in the picture okay
and so I'm going to take this now I'm
going to go down to my pin that is still
on this bulb circuit it's got this red
insulator on the end of it
and what I'm going to do is I'm just
going to touch this on the pin to take a
listen to the system you actually be
able to hear it if this thing starts to
charge
engine just got a little bit lower idle
speed
14:02
my bulb is dim not really relevant for
this take it back off definitely heard
that alternator kick on I'm gonna give
you a voltage reading on the system so
I'll just go back now to this
terminal that I'm using in the back
connected to the battery positive I'll
give you a voltage reading here and I'll
let you guys watch while I'm redoing
this test
okay watch the voltmeter let's connect
14:38
this test light now to this pin
and you can see we're now charging
14 volts I like that this battery is
weak too so once this battery charge is
up a little more that voltage will be a
little higher that's why it's really
bogging this engine down is it's uh in a
way almost full fielding the circuit
dead battery high amperage law 2
horsepower dream
so as I've just shown you guys a bulb
15:17
circuit malfunction can cause an
alternator to not towards I've seen
vehicles come in with this problem that
have had three batteries and three
alternators before they finally gave up
on it because they don't know how to do
proper voltage measurements on an
alternator I've seen this same condition
on a Volkswagen we now see it on a Mazda
I just helped someone on IAT n recently
with this kind of situation this is the
exact test I told him to do with his car
he was having issues with the alternator
15:51
of course and he was concerned about the
cluster and the dash and having to go in
there and check in the bulb circuit and
what I had told him to do is this exact
test and so think about it if you do
this test and that alternator starts to
charge you don't need an alternator you
don't have a wiring problem out here you
definitely need to pull the the
cluster that was his situation where
we're at now we're not ready to do that
let's go inside the car now and take a
16:21
look at what we're missing can't turn
the key on first simple bulb tech
there's nothing we have no indications
on here at all he is in the on position
I'll start it
my gauges are not moving my tachometer
is not moving
I have no turn signals you know these
are all things we were not aware of up
front and I know some of you guys are
thinking that why don't you just check
16:53
the fuses in the first place the point
is this what do you do when you check
the fuses they're all good
you check the wiring to the alternator
it looks like it's good you're not sure
about the bulb circuit that's the point
of knowing how to do this it isn't
always as simple as checking the fuses
and you guys that say that to me you
really don't know what's going on of
course we check the fuses of course we
do those basic checks but in the real
17:26
world it doesn't always go that way and
this could have been like the Volkswagen
that I had done in the past where
everything looked good and it looked
like it needed an alternator what we
focused on that bulb circuit and we had
enough evidence supported by this test
that we're doing with the test light
doing the bypass test that said hey we
have a bulb circuit for sure that's
causing this issue it's time to pull the
cluster and on some of these cars
pulling the cluster is not an easy task
17:58
so think about that for you guys that
have this mentality of oh he show to
check the fuses first that isn't the
point of what we're doing here you know
it isn't always this easy yeah in this
case the fuse was blown as you're going
to see here in a second but guys again
the vision here think about it
everything looks good fuses are good
what do you do now do you have enough
evidence that's the point okay back to
our diagram you see we have a meter fuse
right here that we're worried about and
18:29
it's a 15 amp on a 97 10 amp on a 95 96
and that is in the fusible the fuse
block which is the left kick panel area
so we're going to take a look under
there and see what we find
before we go toward the cluster as a
problem so we're worried about this in
fact with all of those other things not
working
we're pretty sure it's that let's take a
look alright this part is gonna be tough
to shoot here I'm laying underneath this
tiny car using a test light my favorite
19:00
tool for locating blown fuses and all we
were going to do is just run down the
line here look for our light to light
and what we do is we just go on the
backsides of both of the fuses so for
some of you guys that are following me
you're like I know get on with it but
there's others that don't know it's that
simple to check a fuse both sides should
light and just going to go right to it
this one right here we're lit on one
side and we're not lit on the other and
that's our blown fuse now if you have
19:32
any let's go down the line here if we
have any that don't light on either side
that's not necessarily a problem for
example you could have headlight circuit
that's off might be fuse protected I
know honda does that and if you don't
turn the headlights on of course it's
not going to be powered up so we only
worry about no power on both sides of a
fuse whenever that's the circuit that
we're worried about so in our case we're
worried about the meter fuse if our
meter fuse was dead on both sides then
20:05
we would be concerned but in this case
we don't have any circuits like that
anyway we just have this one here this
is definitely a blown fuse so we're
gonna pop this thing out put a new one
in and see the result of that as far as
our charging system and everything else
all right we have the new fuse installed
but turn the key on
you notice we have - lights that we
didn't have before
and I'm gonna start the car let's watch
20:35
our TAC TAC is operating now we do have
a check engine light on this vehicle -
something else that will need to be
looked at let's see if our turn signals
work they do and let's go under the hood
now and see what our charging system
voltage is okay my lead connections I'm
still meter positives going to my jumper
wires going back to the battery and my
meter negative is this black connector
21:09
right here on the valve cover you see on
the reading 14 volts so that is a fix as
far as the charging system goes that the
reason why this thing died on him is
that fuse blew now of course something
caused that use to blow we're going to
have to look at that - I think what I'll
do is I'll make that a separate video
we'll walk through the sorts of ground
tests on this circuit that's if I can
even find it depends how intermittent it
is worst case scenario is we can't
duplicate this as I send him away with
21:39
an extra fuse and come and bring it back
to me if it blows again I work with the
guy so I have that luxury but that's
that's good 14 volts on the charging
system unfortunately guys in our field
there's a lot of people that would have
put an alternator in this already before
doing these checks you know probably put
a battery in it - I get that all the
time you know car comes in with a dead
battery everybody wants to automatically
22:11
replace the battery well here's an
analogy your kid has a power wheel and
you charge it right you plug it in well
when the kid when your kids Power Wheels
battery is dead from driving it do you
replace it every time and the
no I mean sir car batteries aren't meant
to be deep cycled like that but one time
that battery goes dead is not going to
kill it so we don't need to rush and put
batteries in cars and throw parts at
cars and put alternators in again ah I
22:42
know I've said this but I've seen this
kind of symptom with three alternators
and three batteries and just a basket
case by the time that I would get it and
it's got to be aware of it the bulb
circuit is the turn-on for some of these
alternators so while we're talking about
the bulb circuit again why don't we look
at it now with a good working circuit so
we have a good baseline to go by and
what I'll do is I'll get you back on
that bulb circuit wiring we'll look at
23:13
the voltage with the kyo-ahn we'll look
at the voltage with it running and I'll
just keep you where you're at I think
you guys be able to see that
I'm gonna take my
don't lead off the off of the battery
and I'm going to take this down to my
bulb circuit I'll leave my ground
connected where it is this is my bulb
wiring I'm still connected to it from
before
here's your bulb circuit with the engine
running
13.6
23:58
13.7
and let's think about that for a second
we have three wires on this alternator
and I know it's grounded on the housing
and you know the ground issue wasn't the
case with this car something to consider
though - if you have a no targe and all
your voltages are corrected throw a lead
on the housing of the alternator compare
it to battery negative in this case
we're going to want to have a jumper to
go back to the battery it's in the trunk
do a voltage drop test on the case we
don't need to do that here think about
this this car comes in be 80 posts you
24:34
have battery voltage the wire that goes
to the main relay you have battery
voltage and the bulb circuit you have
battery voltage you're done the wiring
is good check the housing for your
ground and then put an alternator in it
so there's your voltage level what's
keeping the bulb off guys is
to power fees
so if you look at this diagram real
quick
we're powered here by this meter fuse
that I just replaced on this side and
then we actually have voltage on this
25:09
side of the circuit too so it's either
the alternator is sending voltage or
we're just not giving it a ground I
don't know enough about the internals of
the regulator to answer that I might be
able to with some other test light tests
let's take a look at it with the key on
engine off and see what it looks like
and remember key on engine off would be
when you want your bulb check all right
we want to see that light light key on
engine off so I'm expecting a ground on
this circuit so let's see what it looks
like just going to reach in turn appeal
that is key on engine off 0.72 of a volt
25:52
and my guess here remember we had point
zero two on this when we started my
guess here is this circuit now has a
ground let's look in the dash see if
this target light is on
yes I do have a charge light that is on
has a little picture of a battery says
charge underneath it and I'm just going
to leave it the way it is take my test
light - battery positive still got my
jumper back here from before what I
26:32
suspect is this light in the light on
this alternator make sure your light
works before you do testing I'm gonna go
down I'm going to touch it on the same
circuit that's in the shot or not and
just rest it on there for a second
all right I have my test light leaning
on that on that pin and you see my light
27:17
is lighting so with the engine off we
have a ground on that circuit okay and
with the engine running there is no
ground on that circuit and again I don't
know the internals of this regulator
that is somehow turning on this voltage
regulator with that missing bulb circuit
this alternator will not charge this
27:48
Mazda is not the only one that does this
Volkswagen Mazda I think I've seen it on
GM I think I've seen it on Ford so be
aware of it I think it's a real good one
real good lesson little voltage drop
measurements in there some alternator
basics pay attention to what you're
doing don't be a parts changer now what
we'll try to do for part two is we'll do
a short to ground test on this meter
fuse and hopefully we can duplicate it
28:20
we'll walk through all the procedures of
how to know what's all on that circuit
what caused it to blow and hopefully we
can duplicate that so for this one
though I'll stop it there blown fuse
again not the final fix we need to find
out what caused that fuse to blow but
the fact is this car did not need a
battery this car did not need an
alternator almost forgot I get these
questions from you guys a lot and I
think it's important to cover it on this
one what kind of test light am i using
28:51
for this using a regular incandescent
bulb type test light I'm not using an
LED test light for this I don't think an
LED test light would work for the bypass
test I showed you I don't think it would
carry enough current to wake up that
voltage regulator so regular
incandescent test light I mean you can
get these at Sears for like 20 bucks so
so hopefully that answers that question
from you guys because I know I get that
a lot so thank you very much hope you
29:25
guys like that
you
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