Voltage Drop Testing the Starter

in this video we're going to quickly

show you how to do a voltage drop test

on the starting system voltage drop

testing on the starting system is very

important if you have a situation where

a starter is cranking slowly you might

not have a bad battery or a bad starter

you might just have a bad connection if

you have a bad connection which of

course can be really common at battery

terminals that are prone to to corrosion

and such then you're not going to be

able to flow as much current because of

the resistance and if your flowing less

current that starter is going to crank

slowly so voltage drop testing the

starter circuit is is very important I'm

in another video we we cover voltage

drop testing the charging system we're

using the same vehicle for the starting

system as we did for the charging system

this is a 2007 Chevy Malibu with a 3.5

liter v6 alright so what we need is a

digital voltmeter which we have here

okay and the other thing that we're

going to need to do to prepare this

vehicle to do this test is we have to

disable the ignition system or the fuel

system because we're going to crank the

engine but we don't want the engine to

start we want to be able to let it crank

for you know five or ten seconds maybe

maybe 15 seconds so that we can get a

reading so we want to disable the the

vehicle from starting now what I've done

actually with this vehicle is instead of

pulling a fuel pump relay or unplugging

the coil pack or something like that

what I've done is I've actually have

actually hooked up a remote start button

and what the what the remote Start

button allows us to do is it allows us

to to crank the engine just by just by

pushing this button so that makes it

good if you're all by yourself working

but it's also good because without the

key ignition switch being turned on we

are just we will will simply be looking

at the you know the the current or the

sorry the voltage drop to and from the

starter without having to have

fuel-system active or the ignition

system active so using it using your

remote start button is a good way to go

and then you don't have to worry about

disabling anything else it doesn't

matter if the ignition switch is on

we're just trying to flow current from

the battery down to the starter and

we're just looking for voltage drop in

in that circuit alone so we're going to

use the remote start button now the

we'll start off with our red lead from

our meter okay we'll take our we'll take

our red lead and you can see it's hooked

up to the the positive battery post okay

now our negative lead is needs to hook

up to the most negative point in the

positive side of that starting system

circuit so the most negative point in

our starting system circuit on the on

the positive side of that circuit is at

the the B terminal at the solenoid so

that on this vehicle is deep down there

so we're going to lift this vehicle up

and then we will hook up our black lead

to the to the starter okay so here we

are down at the starter underneath the

front of this vehicle our black lead

we've got it fished down through there's

a couple things going on right up here

this terminal right here is the the

terminal that actually comes out of the

solenoid there's one right up of right

up above it right up here and this where

this that clamp is connected and that is

our B terminal for the solenoid now this

other this other orange clamp right here

is actually attached to the s terminal

of the solenoid and that's our remote

starter so that's not necessarily part

of this test but this this clamp this

clamp here is going up to the the other

end of the positive battery cable and we

have our black lead attached into into

that red clamp okay so that's how we've

got it that's how we've got it hooked up

here down down at the bottom right at

the starter so with our lead tooked up

we can now crank it and see what our

meter shows us

all right we're looking at our meter

leaves are hooked up let's see what's

going on on the positive side of the

circuit now remember it's always

important when you're doing a voltage

drop test that the circuit be active the

circuit has to be active you can see

we've got the leads hooked up and it

shows zero zero zero zero zero so you

know there's no voltage drop but the

circuit has to be working because we

have to be flowing current in order to

look for voltage drop so that's very

very important to remember when we're

doing an alternator the engines running

when we're doing a starter the engine

has to be cranking so I'm going to take

our a remote start switch and we're

going to crank this engine over for a

little bit and let's see what happens

okay so we got about point one four

point one five volts of drop on the

positive side of this circuit so what's

our specification well once again

positive side of an electrical circuit

generally being being somewhat generous

we are going to allow for half a volt so

0.5 volts 0.5 volts have drop on the

positive side of the circuit and we're

far below that so the positive side of

this circuit has no resistance

it looks like the currents flowing just

fine so now we need to switch our leads

and do the negative side of the circuit

now we've got our red lead up here and

normally we would take this red lead and

we'd go down and touch it to the housing

of the starter but because of the

complications in accessing the starter

down below this vehicle we're just going

to take this red lead and swap it over

to the negative battery post and then

we'll go down underneath the car and

we'll take that black lead and swap it

to the housing of the starter now when

we do the cranking test it's going to

give us a negative number but it doesn't

matter it's the same number as it would

be if we put the leads exactly where

they're supposed to go so we're not

going to worry about that negative

number so for for the sake of

convenience and to make this test a

little easier we're just going to swap

from the positive post to the negative

post now let's go down and swap the

other lead from the the B terminal of

the solenoid

to the housing of the starter so down

underneath the vehicle we took our black

lead and we took it off of the the B

terminal of the solenoid and now it is

attached to it's actually attached to

bolt head on one of one of the bolts

that that hold the starter motor

together and that's fine you know it can

literally be attached anywhere to the

starter housing the only places I kind

of avoid down here are the mounting

bolts for the starter because you know

one of the places where we can add

voltage drop is where those bolts mount

or how the starter mounts to the engine

and if you mount it that if you clip

that black lead onto one of the starter

mounting bolts like like this one right

up here okay that's that's going to have

much better contact with the block so we

want to make sure that the starter

itself has good contact with the block

so we've got our lead down here hooked

up let's go

crank it again okay we got both of our

leads hooked up on the negative side of

the starter circuit I'm going to take

our remote start button will crank this

thing over and let's see how the see if

we've got any resistance or voltage drop

on the negative side of this starter


Oh point zero six point zero six so

what's the specification is that a good

number point zero six specification on

the ground side of this circuit 0.2

volts so point five on the positive side

point two on the negative side so on the

negative side of the circuit if point

two is our maximum and we're at point

zero six then obviously there is no

voltage drop on the negative side of

this circuit so looks pretty good both

the positive side and the negative side

of the circuit are good we know that the

the ground cables are good we know that

the the positive cable is good all the

connections in between we know that all

of those things are good so that is how

you test voltage drop on the starting

system okay pretty simple test ought to

be done anytime a starter is replaced in

order to make sure that that everything

is all that all the wiring is good and

that that you're not missing something

and to make sure that you're thorough in

your diagnosis and of course that's what

we want to do because we want to we want

to be accurate as automotive technicians

we want to do things the right way