Four electrical questions

Hi, I finally was able to make my own jumper wires and successfully test my
blower motor and fan motor; however, I have some questions now:

1) When I went to jumper my blower motor to my battery, I only needed one
wire from the positive prong of the motor to the battery, even though there
is a negative wire coming from the wire cluster to the motor, which attaches
to a bolted on prong on the blower motor body. Why do they have both a
positive and negative wire for the blower motor if you only need the
positive to run the motor?

2) I need a way to securely attached a jumper wire to a female electrical
connector, where the terminals are recessed, and there may be a lot of free
space around them (so any test lead will not stay put while you move your
body elsewhere).

Right now, I use alligator clips to connect to regular prongs/plugs (like on
my blower motor) and paper clips to connect the terminals of a male
electrical connectors (you just plug in the paper clip next to the terminal,
and it stays put).

3) If I am using 20-gauge test lead wire right now from Radio Shack as
jumper wire, will this gauge be thick enough to safely test motors like fan
motors? I have a spool of 14-gauge thin stranded wire from Lowe's, but this
is not that flexible. Radio Shack recommends 10-gauge wire for automotive
uses though.

4) Is an inline fuse really necessary for jumper wires? You can get them at
Radio Shack, but they are expensive.

Thanks for any help!

Julie

Julie P. > wrote in message
news:10ydf.6024$5R4.1050@trnddc06...
> Hi, I finally was able to make my own jumper wires and successfully test
my
> blower motor and fan motor; however, I have some questions now:
>
> 1) When I went to jumper my blower motor to my battery, I only needed one
> wire from the positive prong of the motor to the battery, even though
there
> is a negative wire coming from the wire cluster to the motor, which
attaches
> to a bolted on prong on the blower motor body. Why do they have both a
> positive and negative wire for the blower motor if you only need the
> positive to run the motor?

Because anything electrical will already be earthed back to the battery via
a connection to the chassis or else it wouldn't run in normal operation. If
you connect a direct positive feed and the device runs it tells you that
both the device and the earth side is ok. If the device still doesn't run it
could either be broken or the earth side is not making contact. In that case
you need to add a negative feed to check the device fully.
--
Dave Baker

"Dave Baker" > wrote in message
...
>
> Julie P. > wrote in message
> news:10ydf.6024$5R4.1050@trnddc06...
>> Hi, I finally was able to make my own jumper wires and successfully test
> my
>> blower motor and fan motor; however, I have some questions now:
>>
>> 1) When I went to jumper my blower motor to my battery, I only needed one
>> wire from the positive prong of the motor to the battery, even though
> there
>> is a negative wire coming from the wire cluster to the motor, which
> attaches
>> to a bolted on prong on the blower motor body. Why do they have both a
>> positive and negative wire for the blower motor if you only need the
>> positive to run the motor?
>
> Because anything electrical will already be earthed back to the battery
> via
> a connection to the chassis or else it wouldn't run in normal operation.
> If
> you connect a direct positive feed and the device runs it tells you that
> both the device and the earth side is ok. If the device still doesn't run
> it
> could either be broken or the earth side is not making contact. In that
> case
> you need to add a negative feed to check the device fully.
> --
> Dave Baker
>

Thanks Dave! Ok, this makes sense, as the blower motor is mounted in a metal
duct whihc is connected to the firewall. And it did test ok (it was brand
new--it better have ).

But when I tired the same test with just one positive wire for my radiator
fan, it did not work, not until I also connected the negative wire. Maybe
because the fan motor is encased in a plastic support frame?

Julie

> 2) I need a way to securely attached a jumper wire to a female electrical
> connector, where the terminals are recessed, and there may be a lot of free
> space around them (so any test lead will not stay put while you move your
> body elsewhere).

You can probably clip the aligator to a nail and stick that in the socket. I
use a piece of thick heavy bared copper wire.

As for the radiator fan motor not comming on when you probe it, that might
be due to the location of the thermal switch which only completes the
circuit when the rad heats up. I don't know enough about them to say for
sure.


>
> Right now, I use alligator clips to connect to regular prongs/plugs (like on
> my blower motor) and paper clips to connect the terminals of a male
> electrical connectors (you just plug in the paper clip next to the terminal,
> and it stays put).
>
> 3) If I am using 20-gauge test lead wire right now from Radio Shack as
> jumper wire, will this gauge be thick enough to safely test motors like fan
> motors? I have a spool of 14-gauge thin stranded wire from Lowe's, but this
> is not that flexible. Radio Shack recommends 10-gauge wire for automotive
> uses though.
>
> 4) Is an inline fuse really necessary for jumper wires? You can get them at
> Radio Shack, but they are expensive.
>
> Thanks for any help!
>
> Julie
>
>


--
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"Julie P." > wrote in message
news:10ydf.6024$5R4.1050@trnddc06...
> Hi, I finally was able to make my own jumper wires and successfully
> test my blower motor and fan motor; however, I have some questions
> now:
>
> 1) When I went to jumper my blower motor to my battery, I only needed
> one wire from the positive prong of the motor to the battery, even
> though there is a negative wire coming from the wire cluster to the
> motor, which attaches to a bolted on prong on the blower motor body.
> Why do they have both a positive and negative wire for the blower
> motor if you only need the positive to run the motor?

Many auto items even lamps have both a positive drive wire and a (Often
black) ground wire thei ensures the ground stays good even in old age
when the mounting frame connection has rusted.


> 3) If I am using 20-gauge test lead wire right now from Radio Shack as
> jumper wire, will this gauge be thick enough to safely test motors
> like fan motors? I have a spool of 14-gauge thin stranded wire from
> Lowe's, but this is not that flexible. Radio Shack recommends 10-gauge
> wire for automotive uses though.

If you only use it for testing and stop when it burns your fingers it
will be fairly safe.

For a permanent rewire you should use wire as thick as was there from
the factory.


> 4) Is an inline fuse really necessary for jumper wires? You can get
> them at Radio Shack, but they are expensive.

An inline fuse right close to the battery connection could save you from
connecting to a wrong pin and starting a fire in the test lead.
--
John G

Wot's Your Real Problem?

Julie P. wrote:

>Hi, I finally was able to make my own jumper wires and successfully test my
>blower motor and fan motor; however, I have some questions now:

I've only got one question.

Why not use a test lamp (low wattage bulb with earth lead attached)
rather than jumper leads? In most cases it'll tell you as much, and
more, with a lot less risk of setting your car alight. Or worse
still, providing a path for the smoke to escape from delicate
electronic components -- around which an LED is an even safer option.

Jumper leads can be fine for bench testing but need to be used with
extreme caution for in car diagnostics.

--
John H

"William R. Watt" > wrote in message
...
>
>> 2) I need a way to securely attached a jumper wire to a female electrical
>> connector, where the terminals are recessed, and there may be a lot of
>> free
>> space around them (so any test lead will not stay put while you move your
>> body elsewhere).
>
> You can probably clip the aligator to a nail and stick that in the socket.
> I
> use a piece of thick heavy bared copper wire.
>

Thanks William. What I meant was is there a way to get a secure connection,
so I can free up my hands and body to do something else if need be? Right
now, I use a paper clip, which works, but it won't stay in place if need be.

> As for the radiator fan motor not comming on when you probe it, that might
> be due to the location of the thermal switch which only completes the
> circuit when the rad heats up. I don't know enough about them to say for
> sure.
>

Oh, the fan comes on ok, when both positive and negative are jumpered. I am
just trying to find a way to test my coolant temperature sensor now. My
manual has some instructions, so I will have to check there.

Julie

"John_H" > wrote in message
...

> I've only got one question.
>
> Why not use a test lamp (low wattage bulb with earth lead attached)
> rather than jumper leads? In most cases it'll tell you as much, and
> more, with a lot less risk of setting your car alight. Or worse
> still, providing a path for the smoke to escape from delicate
> electronic components -- around which an LED is an even safer option.
>
> Jumper leads can be fine for bench testing but need to be used with
> extreme caution for in car diagnostics.
>
> --
> John H

Usually a test lamp will only tell you if you have voltage present, not if
the motor
will run when connected to the electrical source. Test lamps are handy
items, but
not necessarily for this.

By the way, Julie, you can get in inline fuse holder at Autozone for a
couple of bucks.
Maybe that is more than you would like to spend.

> wrote in message
om...
>
> "John_H" > wrote in message
> ...
>
>> I've only got one question.
>>
>> Why not use a test lamp (low wattage bulb with earth lead attached)
>> rather than jumper leads? In most cases it'll tell you as much, and
>> more, with a lot less risk of setting your car alight. Or worse
>> still, providing a path for the smoke to escape from delicate
>> electronic components -- around which an LED is an even safer option.
>>
>> Jumper leads can be fine for bench testing but need to be used with
>> extreme caution for in car diagnostics.
>>
>> --
>> John H
>
> Usually a test lamp will only tell you if you have voltage present, not if
> the motor
> will run when connected to the electrical source. Test lamps are handy
> items, but
> not necessarily for this.
>
> By the way, Julie, you can get in inline fuse holder at Autozone for a
> couple of bucks.
> Maybe that is more than you would like to spend.
>
>

Thanks. They were $11.49 each at Radio shack, and I had been considering
making 6-8 jumper wires, necessitating spending $75-$95, which seemed a bit
much. So the AZ one sounds like a better deal. Anyway, I have to save money,
in case I end up having to do costly engine repairs due to the low oil
pressure problem.

Julie

"John G" > wrote in message
...
>
> "Julie P." > wrote in message
> news:10ydf.6024$5R4.1050@trnddc06...
>> Hi, I finally was able to make my own jumper wires and successfully test
>> my blower motor and fan motor; however, I have some questions now:
>>
>> 1) When I went to jumper my blower motor to my battery, I only needed one
>> wire from the positive prong of the motor to the battery, even though
>> there is a negative wire coming from the wire cluster to the motor, which
>> attaches to a bolted on prong on the blower motor body. Why do they have
>> both a positive and negative wire for the blower motor if you only need
>> the positive to run the motor?
>
> Many auto items even lamps have both a positive drive wire and a (Often
> black) ground wire thei ensures the ground stays good even in old age when
> the mounting frame connection has rusted.
>

Ok, nice redundancy feature I guess. Surprising for a Chevy Cavalier though.

>
>> 3) If I am using 20-gauge test lead wire right now from Radio Shack as
>> jumper wire, will this gauge be thick enough to safely test motors like
>> fan motors? I have a spool of 14-gauge thin stranded wire from Lowe's,
>> but this is not that flexible. Radio Shack recommends 10-gauge wire for
>> automotive uses though.
>
> If you only use it for testing and stop when it burns your fingers it will
> be fairly safe.
>

My fear is I am always tempted to grap the paper clips stuck in the
alligator clips, which are long and wobbly, so I can stick them more easily
into male terminals. But if the wires are live, I could be in for quite
shock.

Thanks John,

Julie