Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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Old February 10th 20, 01:31 AM posted to sci.electronics.repair
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Default How to Test a Relay


My car's blower motor relay may be bad (or the cause of noisy fan). So I
found the following video...

How to Test a Relay the Correct Way
https://www.youtube.com/watch?v=ire7vyDqelg

However, I don't have a cordless drill battery (used in the video).
Will the following battery charger...

UPG D1724 Sealed Lead Acid Battery Charger (6V/12V Switchable Single-
Stage With Alligator Clips)
https://www.amazon.com/gp/product/B0...c_act_title_1?
smid=A10QFO4IXVZNRN&psc=1

work ? Other frugal ideas ?

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Old February 10th 20, 02:06 AM posted to sci.electronics.repair
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First recorded activity by DIYBanter: Sep 2008
Posts: 104
Default How to Test a Relay

On 2/9/2020 7:31 PM, Adam wrote:

My car's blower motor relay may be bad (or the cause of noisy fan). So I
found the following video...

How to Test a Relay the Correct Way
https://www.youtube.com/watch?v=ire7vyDqelg

However, I don't have a cordless drill battery (used in the video).
Will the following battery charger...

UPG D1724 Sealed Lead Acid Battery Charger (6V/12V Switchable Single-
Stage With Alligator Clips)
https://www.amazon.com/gp/product/B0...c_act_title_1?
smid=A10QFO4IXVZNRN&psc=1

work ? Other frugal ideas ?

An automotive cube uses 12 volts. Any 12 volt DC source will see if the
coil pulls in the contacts.
There is much more to checking a relay properly.
Pull in current, dropout current, contact resistance, and more.
But if just want to see if you can hear the armature pull in that it
will do that.
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Old February 10th 20, 02:38 AM posted to sci.electronics.repair
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Posts: 17
Default How to Test a Relay

On Sun, 09 Feb 2020 20:06:16 -0500, Tom Biasi wrote:

On 2/9/2020 7:31 PM, Adam wrote:

My car's blower motor relay may be bad (or the cause of noisy fan). So
I found the following video...

How to Test a Relay the Correct Way
https://www.youtube.com/watch?v=ire7vyDqelg

However, I don't have a cordless drill battery (used in the video).
Will the following battery charger...

UPG D1724 Sealed Lead Acid Battery Charger (6V/12V Switchable Single-
Stage With Alligator Clips)
https://www.amazon.com/gp/product/B0...c_act_title_1?
smid=A10QFO4IXVZNRN&psc=1

work ? Other frugal ideas ?

An automotive cube uses 12 volts. Any 12 volt DC source will see if the
coil pulls in the contacts.
There is much more to checking a relay properly.
Pull in current, dropout current, contact resistance, and more.
But if just want to see if you can hear the armature pull in that it
will do that.


According to the video, I think I also need to check resistance.

Will that battery charger on Amazon work ?
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Old February 10th 20, 03:34 AM posted to sci.electronics.repair
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Posts: 104
Default How to Test a Relay

On 2/9/2020 8:38 PM, Adam wrote:
On Sun, 09 Feb 2020 20:06:16 -0500, Tom Biasi wrote:

On 2/9/2020 7:31 PM, Adam wrote:

My car's blower motor relay may be bad (or the cause of noisy fan). So
I found the following video...

How to Test a Relay the Correct Way
https://www.youtube.com/watch?v=ire7vyDqelg

However, I don't have a cordless drill battery (used in the video).
Will the following battery charger...

UPG D1724 Sealed Lead Acid Battery Charger (6V/12V Switchable Single-
Stage With Alligator Clips)
https://www.amazon.com/gp/product/B0...c_act_title_1?
smid=A10QFO4IXVZNRN&psc=1

work ? Other frugal ideas ?

An automotive cube uses 12 volts. Any 12 volt DC source will see if the
coil pulls in the contacts.
There is much more to checking a relay properly.
Pull in current, dropout current, contact resistance, and more.
But if just want to see if you can hear the armature pull in that it
will do that.


According to the video, I think I also need to check resistance.

Will that battery charger on Amazon work ?

Any 12 vdc source will work.
to check coil resistance you need an ohm meter.
The relay in the video has a diode.
So ohm meter polarity is important.
In a proper test the diode characteristics would also be checked.
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Old February 10th 20, 04:32 AM posted to sci.electronics.repair
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Posts: 1,949
Default How to Test a Relay

On Sunday, February 9, 2020 at 4:31:52 PM UTC-8, Adam wrote:
My car's blower motor relay may be bad (or the cause of noisy fan).


However, I don't have a cordless drill battery (used in the video).


You have a car, with a battery that makes perfectly acceptable 12V.

Will the following battery charger...

UPG D1724 Sealed Lead Acid Battery Charger (6V/12V Switchable Single-
Stage With Alligator Clips)
work ?


Maybe. It's possible to make chargers that don't generate +12V unless
attached to a battery, or that turn off if/when peak voltage exceeds a full battery charge.


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Old February 10th 20, 04:39 AM posted to sci.electronics.repair
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Default How to Test a Relay

On Sun, 09 Feb 2020 19:32:13 -0800, whit3rd wrote:

On Sunday, February 9, 2020 at 4:31:52 PM UTC-8, Adam wrote:
My car's blower motor relay may be bad (or the cause of noisy fan).


However, I don't have a cordless drill battery (used in the video).


You have a car, with a battery that makes perfectly acceptable 12V.


Maybe best to just use the car battery then. Just connect with alligator
clips.


Will the following battery charger...

UPG D1724 Sealed Lead Acid Battery Charger (6V/12V Switchable Single-
Stage With Alligator Clips)
work ?


Maybe. It's possible to make chargers that don't generate +12V unless
attached to a battery, or that turn off if/when peak voltage exceeds a
full battery charge.


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Old February 10th 20, 07:40 AM posted to sci.electronics.repair
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First recorded activity by DIYBanter: Jul 2006
Posts: 827
Default How to Test a Relay

On 2020/02/09 4:31 p.m., Adam wrote:

My car's blower motor relay may be bad (or the cause of noisy fan). So I
found the following video...

How to Test a Relay the Correct Way
https://www.youtube.com/watch?v=ire7vyDqelg

However, I don't have a cordless drill battery (used in the video).
Will the following battery charger...

UPG D1724 Sealed Lead Acid Battery Charger (6V/12V Switchable Single-
Stage With Alligator Clips)
https://www.amazon.com/gp/product/B0...c_act_title_1?
smid=A10QFO4IXVZNRN&psc=1

work ? Other frugal ideas ?


OK, the video is fine as far as it goes, but it really is not the last
word in properly testing a relay as the real test is do the contacts
work under load.

So, what I would do if I was suspicious of this relay, and I didn't want
to remove the cover to visually inspect the contacts, is I would first
hook the relay to 12VDC with the +12VDC source connected to terminal 86,
and the negative side of the 12VDC supply to terminal 87. The diode
shown in the wiring diagram on the relay shows that the relay will not
operated if these are wired backwards as the diode would block the
current flow.

Next I would find a load of a couple of amps - perhaps a car light bulb.
You want something that is 24Watts - which is roughly 2 amps at 12VDC.
You then wire up the lamp so that the switch inside the relay - contacts
30 & 87 - are in series with the light and the 12VDC source. And you
also hook up a voltmeter across terminals 30 & 87 - to measure voltage
across the contacts.

Now power/energize the relay - the 12V lamp should light and the voltage
across the terminals 30 & 87 should drop to as close to zero VDC as
possible. Anything under 0.100VDC would probably be OK, with actually
0.00VDC being the ideal. If you see around 0.50 or more VDC across those
two terminals then the relay contacts are corroded and the relay is
unlikely to operate anything drawing heavier current well at all. It
should be replaced.

Without testing relay contacts under a reasonable load you really don't
know if the contacts will operate well enough to do the job that is
required. These relays are usually rated at around 25A, so a 2A load is
roughly ten percent and will give you some idea of the contact condition
if you measure the voltage drop across them.

John :-#)#
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Old February 10th 20, 07:41 AM posted to sci.electronics.repair
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Posts: 827
Default How to Test a Relay

On 2020/02/09 4:31 p.m., Adam wrote:

My car's blower motor relay may be bad (or the cause of noisy fan). So I
found the following video...

How to Test a Relay the Correct Way
https://www.youtube.com/watch?v=ire7vyDqelg

However, I don't have a cordless drill battery (used in the video).
Will the following battery charger...

UPG D1724 Sealed Lead Acid Battery Charger (6V/12V Switchable Single-
Stage With Alligator Clips)
https://www.amazon.com/gp/product/B0...c_act_title_1?
smid=A10QFO4IXVZNRN&psc=1

work ? Other frugal ideas ?


Oh, and it is really unlikely that a relay will cause a fan to be noisy
- that is more likely bearing failure, or foreign matter in the motor
assembly somewhere...

John :-#)#
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Old February 10th 20, 12:09 PM posted to sci.electronics.repair
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First recorded activity by DIYBanter: Jan 2015
Posts: 11,325
Default How to Test a Relay

On Monday, 10 February 2020 00:31:52 UTC, Adam wrote:
My car's blower motor relay may be bad (or the cause of noisy fan). So I
found the following video...

How to Test a Relay the Correct Way
https://www.youtube.com/watch?v=ire7vyDqelg

However, I don't have a cordless drill battery (used in the video).
Will the following battery charger...

UPG D1724 Sealed Lead Acid Battery Charger (6V/12V Switchable Single-
Stage With Alligator Clips)
https://www.amazon.com/gp/product/B0...c_act_title_1?
smid=A10QFO4IXVZNRN&psc=1

work ? Other frugal ideas ?


Nearly all relay failures are switching points gone high resistance. So test that. To power the coil... you have a car battery right?
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Old February 10th 20, 01:27 PM posted to sci.electronics.repair
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First recorded activity by DIYBanter: Dec 2014
Posts: 17
Default How to Test a Relay

On Sun, 09 Feb 2020 22:41:33 -0800, John Robertson wrote:

On 2020/02/09 4:31 p.m., Adam wrote:

My car's blower motor relay may be bad (or the cause of noisy fan). So
I found the following video...

How to Test a Relay the Correct Way
https://www.youtube.com/watch?v=ire7vyDqelg

However, I don't have a cordless drill battery (used in the video).
Will the following battery charger...

UPG D1724 Sealed Lead Acid Battery Charger (6V/12V Switchable Single-
Stage With Alligator Clips)
https://www.amazon.com/gp/product/B0...c_act_title_1?
smid=A10QFO4IXVZNRN&psc=1

work ? Other frugal ideas ?


Oh, and it is really unlikely that a relay will cause a fan to be noisy
- that is more likely bearing failure, or foreign matter in the motor
assembly somewhere...

John :-#)#


Blower Motor
https://us.lexusownersclub.com/forum...-blower-motor/

Relays are cheap compared to other parts so I don't mind starting with
the relay.


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