Re: Stus-List Problem with 2 new fuel gauges...long story

[Leslie Paal via CnC-List]

just to split hairs, the link forgot one, important thing.  The coil is 
connected to a spring and the current introduced force is acting against the 
spring.  More current more force bigger deflection.  If the spring was not 
there the needle would be pegged against the end stop and 'never' come back.

Leslie.
(finally some use for my science degrees) ;-)


On Sat, 4/4/15, Josh Muckley via CnC-List  wrote:

 Subject: Re: Stus-List Problem with 2 new fuel gauges...long story
 To: "C&C List" , "Marek Dziedzic" 

 Date: Saturday, April 4, 2015, 9:53 PM
 
 
 
 Excerpt from the following link:
 
 http://www.doityourself.com/stry/how-does-an-analog-voltmeter-work
 An analog voltmeter works by passing a current
 through a coil that is suspended between two permanent
 magnets. This coil of wire is known as a moving coil since
 it moves in relation to the permanent magnets when a voltage
 is applied. When a voltage is applied and the voltage scale
 is chosen, a resistor of known value is placed in series
 with the measurement leads. This way Ohm’s Law can be
 applied. The applied voltage through the coil creates a
 magnetic field which acts against the permanent magnets that
 the pointer pivot is placed between. This magnetic field
 causes a corresponding deflection of the pointer. This
 pointer deflection will be in direct proportion to the
 amount of voltage being applied to the moving coil wrapping
 the pointer pivot. Once pointer oscillation has stopped,
 accurate readings can be made.
 
 So to summerize:  Yes Marek, basic analog
 meter movement is caused by current flow through the meter
 coil.
 I suppose in a a way that makes all anaolog
 coil meters "current" meters.  I referred to the
 fuel gage as a voltage meter so as to suggest that with the
 meter completely removed from the boat a "voltage"
 applied across the terminals from sense to ground or sense
 to vcc (+12v terminal) would cause meter deflection.  In
 order to troubleshoot one might select a common 6v lantern
 battery for this task.
 Using the attached drawing as a referance and
 understanding that R2 is the fuel level sender and
 "D" is the sender "sensing" terminal on
 the meter.  I believe that inadvertently swapping the +12v
 and sense lines or swapping the ground and +12v lines would
 cause the symptom of the fuel gage needle pegging low.
 To both our points, the attached picture
 suggests that the meter being used is a voltage meter (Vg)
 and referances the current from points D to B (Ig) as
 driving its movement.
 Josh
 On Apr 4, 2015 10:40
 PM, "Marek Dziedzic via CnC-List" 
 wrote:
 
 
 
 
 
 
 Josh,
 
 
 
 This is certainly not sailing related, but if i remember it
 correctly, they are all really ammeters (the current flowing
 through them creates the magnetic field that moves the
 needle). 
 
 
 
 
 Marek
 
 
 
 
 Josh Muckley via CnC-List wrote:
 
 
 
 
 
 All analog meters are just measuring the
 "voltage drop" across a resistance.  The key is
 to have the appropriate voltage input +12v.  If the +12v
 and the sensing line were reversed then the "voltage
 drop" would be "negative" driving the needle
  to the empty peg.
 Josh
 On Apr 4, 2015 7:08 PM, "Wally Bryant via
 CnC-List" 
 wrote:
 
 
 I thought they were Ohm meters. Anyway, I just Googled it to
 make sure, and see a ton of pages on testing marine fuel
 sender resistance.
 
 
 
 Wal
 
 
 
 you wrote:
 
 
 I agree with your diagnosis.  It's gotta be reversed
 polarity...of the
 
 sense and gnd.  Fundamentally the fuel gages are just
 voltage meters.  They
 
 respond proportionally to the voltage drop across the
 variable resistance
 
 in the sender.  I would disconnect the leads and use an ohm
 meter to
 
 measure and validate the resistance of the senders. 
 Switching the polarity
 
 of the sense and gnd monetarily probably won't break
 anything.  Before
 
 doing so validate that your wiring looks like the attached
 picture.
 
 
 
 
 
 
 ___
 
 
 
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 CnC-List@cnc-list.com
 
 To change your list preferences, including unsubscribing --
 go to the bottom of page at:
 
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 unsubscribing -- go to the bottom of page at:
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Re: Stus-List Problem with 2 new fuel gauges...long story

[Leslie Paal via CnC-List]

they measure the current.  I don't think you notice any real voltage drop on 
the battery when the fuel level changes...  ;-)

You are correct about the reversed polarity.

Leslie.


On Sat, 4/4/15, Josh Muckley via CnC-List  wrote:

 Subject: Re: Stus-List Problem with 2 new fuel gauges...long story
 To: w...@wbryant.com, "C&C List" 
 Date: Saturday, April 4, 2015, 6:13 PM
 
 All analog
 meters are just measuring the "voltage drop"
 across a resistance.  The key is to have the appropriate
 voltage input +12v.  If the +12v and the sensing line were
 reversed then the "voltage drop" would be
 "negative" driving the needle to the empty
 peg.
 Josh
 On Apr 4, 2015 7:08 PM,
 "Wally Bryant via CnC-List" 
 wrote:
 I thought
 they were Ohm meters. Anyway, I just Googled it to make
 sure, and see a ton of pages on testing marine fuel sender
 resistance.
 
 
 
 Wal
 
 
 
 you wrote:
 
 
 I agree with your diagnosis.  It's gotta be reversed
 polarity...of the
 
 sense and gnd.  Fundamentally the fuel gages are just
 voltage meters.  They
 
 respond proportionally to the voltage drop across the
 variable resistance
 
 in the sender.  I would disconnect the leads and use an ohm
 meter to
 
 measure and validate the resistance of the senders. 
 Switching the polarity
 
 of the sense and gnd monetarily probably won't break
 anything.  Before
 
 doing so validate that your wiring looks like the attached
 picture.
 
 
 
 
 
 
 ___
 
 
 
 Email address:
 
 CnC-List@cnc-list.com
 
 To change your list preferences, including unsubscribing --
 go to the bottom of page at:
 
 http://cnc-list.com/mailman/listinfo/cnc-list_cnc-list.com
 
 
 
 
 -Inline Attachment Follows-
 
 ___
 
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 CnC-List@cnc-list.com
 To change your list preferences, including
 unsubscribing -- go to the bottom of page at:
 http://cnc-list.com/mailman/listinfo/cnc-list_cnc-list.com
 
 

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Re: Stus-List Problem with 2 new fuel gauges...long story

[Leslie Paal via CnC-List]

strictly speaking the fuel gauge measures current.  ;-)

Leslie.


On Sat, 4/4/15, Wally Bryant via CnC-List  wrote:

 Subject: Re: Stus-List Problem with 2 new fuel gauges...long story
 To: cnc-list@cnc-list.com
 Date: Saturday, April 4, 2015, 4:07 PM
 
 I thought they were Ohm
 meters. Anyway, I just Googled it to make sure, 
 and see a ton of pages on testing marine fuel
 sender resistance.
 
 Wal
 
 you wrote:
 > I agree with
 your diagnosis.  It's gotta be reversed polarity...of
 the
 > sense and gnd.  Fundamentally the
 fuel gages are just voltage meters.  They
 > respond proportionally to the voltage drop
 across the variable resistance
 > in the
 sender.  I would disconnect the leads and use an ohm meter
 to
 > measure and validate the resistance
 of the senders.  Switching the polarity
 > of the sense and gnd monetarily probably
 won't break anything.  Before
 >
 doing so validate that your wiring looks like the attached
 picture.
 
 
 ___
 
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 unsubscribing -- go to the bottom of page at:
 http://cnc-list.com/mailman/listinfo/cnc-list_cnc-list.com
 
 

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Re: Stus-List Problem with 2 new fuel gauges...long story

[Robert Boyer via CnC-List]

One terminal of the sender connects to the plate that mounts to the tank--this 
is grounded because the tank is grounded.  So, polarity is involved here.  I 
can remove the tank ground and switch the wires.

Bob Boyer
S/V Rainy Days / Annapolis MD
1983 C&C Landfall 38 - Hull #230
email: dainyr...@icloud.com 
blog: dainyrays.blogspot.com

"There is nothing--absolutely nothing--half so much worth doing as simply 
messing about in boats."  --Kenneth Grahame

> On Apr 5, 2015, at 1:06 AM, Josh Muckley  wrote:
> 
> The sender doesn't have a polarity.  It is just a resistance.  Is this what 
> the back of your sender looks like?  Which wires do you have attached where?
> 
> Josh
> 
>> On Apr 4, 2015 10:49 PM, "Robert Boyer via CnC-List"  
>> wrote:
>> When you connect the sensing wire to ground, the needle goes positive all 
>> the way as it should do but it does not register the fuel level.
>> 
>> I now believe that one gauge is working correctly because the needle moved 
>> slightly positive when energized--but the tank is completely empty.
>> 
>> The other gauge is hooked up the same way but I think the wires inside the 
>> tank sender is reversed, which makes the needle go in the wrong direction.  
>> I remove the ground from the sender and reverse the sender polarity tomorrow.
>> 
>> Wal, would I also have to reverse the power supply polarity on the gauge to 
>> make it work properly?
>> 
>> Thanks!
>> 
>> Bob
>> 
>> Bob Boyer
>> S/V Rainy Days / Annapolis MD
>> 1983 C&C Landfall 38 - Hull #230
>> email: dainyr...@icloud.com 
>> blog: dainyrays.blogspot.com
>> 
>> "There is nothing--absolutely nothing--half so much worth doing as simply 
>> messing about in boats."  --Kenneth Grahame
>> 
>>> On Apr 4, 2015, at 10:40 PM, Marek Dziedzic via CnC-List 
>>>  wrote:
>>> 
>>> Josh,
>>> 
>>> This is certainly not sailing related, but if i remember it correctly, they 
>>> are all really ammeters (the current flowing through them creates the 
>>> magnetic field that moves the needle).  
>>> 
>>> Marek
>>> 
>>> 
>>> 
>>> Josh Muckley via CnC-List wrote:
>>> 
>>> 
>>> All analog meters are just measuring the "voltage drop" across a 
>>> resistance.  The key is to have the appropriate voltage input +12v.  If the 
>>> +12v and the sensing line were reversed then the "voltage drop" would be 
>>> "negative" driving the needle to the empty peg.
>>> 
>>> Josh
>>> 
>>> On Apr 4, 2015 7:08 PM, "Wally Bryant via CnC-List"  
>>> wrote:
>>> I thought they were Ohm meters. Anyway, I just Googled it to make sure, and 
>>> see a ton of pages on testing marine fuel sender resistance.
>>> 
>>> Wal
>>> 
>>> you wrote:
>>> I agree with your diagnosis.  It's gotta be reversed polarity...of the
>>> sense and gnd.  Fundamentally the fuel gages are just voltage meters.  They
>>> respond proportionally to the voltage drop across the variable resistance
>>> in the sender.  I would disconnect the leads and use an ohm meter to
>>> measure and validate the resistance of the senders.  Switching the polarity
>>> of the sense and gnd monetarily probably won't break anything.  Before
>>> doing so validate that your wiring looks like the attached picture.
>>> 
>>> 
>>> ___
>>> 
>>> Email address:
>>> CnC-List@cnc-list.com
>>> To change your list preferences, including unsubscribing -- go to the 
>>> bottom of page at:
>>> http://cnc-list.com/mailman/listinfo/cnc-list_cnc-list.com
>>> 
>>> ___
>>> 
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>>> bottom of page at:
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>> 
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> <$_3.JPG>
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Re: Stus-List Problem with 2 new fuel gauges...long story

[Don Newman via CnC-List]

The actual meter portion of analog meters are essentially the same (Volt,
Amp, Ohm) they register the voltage presented to them.  The way the are
placed in the circuit makes the difference.  Volt meter across the voltage,
Amp across a shunt (a low resistance resistor) to measure the voltage drop
across the shunt and Ohm has its own power supply to measure resistors.

The normal setup for fuel tanks is for the meter to be supplied with the +
voltage and one side of the the variable resistor in the tank  connected to
the meter and the other to ground.  In the case of a metal tank such as in
an automobile the tank itself is grounded so there is no need for a second
lead.  If the tank is plastic then a ground lead is needed to the frame of
the sensor assembly.

If there is no connection to ground then the meter should not move.

You said you measured the resistance across the sensor on one tank.  Is
this the one you think is failing?
If not you can measure the sense line to ground to check the resistance on
the one you think is failing.
If it is the new tank that is failing are you sure that on the tank sensor,
one side is connected to ground and the other to your meter?

You could try to find something in the 100 ohm range to test the meter -
light bulb etc.

Good luck.

Don Newman
C&C 44
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Re: Stus-List Problem with 2 new fuel gauges...long story

[Josh Muckley via CnC-List]

The sender doesn't have a polarity.  It is just a resistance.  Is this what
the back of your sender looks like?  Which wires do you have attached where?

Josh
On Apr 4, 2015 10:49 PM, "Robert Boyer via CnC-List" 
wrote:

> When you connect the sensing wire to ground, the needle goes positive all
> the way as it should do but it does not register the fuel level.
>
> I now believe that one gauge is working correctly because the needle moved
> slightly positive when energized--but the tank is completely empty.
>
> The other gauge is hooked up the same way but I think the wires inside the
> tank sender is reversed, which makes the needle go in the wrong direction.
> I remove the ground from the sender and reverse the sender polarity
> tomorrow.
>
> Wal, would I also have to reverse the power supply polarity on the gauge
> to make it work properly?
>
> Thanks!
>
> Bob
>
> Bob Boyer
> S/V Rainy Days / Annapolis MD
> 1983 C&C Landfall 38 - Hull #230
> email: dainyr...@icloud.com
> blog: dainyrays.blogspot.com
>
> "There is nothing--absolutely nothing--half so much worth doing as simply
> messing about in boats."  --Kenneth Grahame
>
> On Apr 4, 2015, at 10:40 PM, Marek Dziedzic via CnC-List <
> cnc-list@cnc-list.com> wrote:
>
> Josh,
>
> This is certainly not sailing related, but if i remember it correctly,
> they are all really ammeters (the current flowing through them creates the
> magnetic field that moves the needle).
>
> Marek
>
>
>
> Josh Muckley via CnC-List wrote:
>
>  All analog meters are just measuring the "voltage drop" across a
> resistance.  The key is to have the appropriate voltage input +12v.  If the
> +12v and the sensing line were reversed then the "voltage drop" would be
> "negative" driving the needle to the empty peg.
>
> Josh
> On Apr 4, 2015 7:08 PM, "Wally Bryant via CnC-List" 
> wrote:
>
> I thought they were Ohm meters. Anyway, I just Googled it to make sure,
> and see a ton of pages on testing marine fuel sender resistance.
>
> Wal
>
> you wrote:
>
> I agree with your diagnosis.  It's gotta be reversed polarity...of the
> sense and gnd.  Fundamentally the fuel gages are just voltage meters.  They
> respond proportionally to the voltage drop across the variable resistance
> in the sender.  I would disconnect the leads and use an ohm meter to
> measure and validate the resistance of the senders.  Switching the polarity
> of the sense and gnd monetarily probably won't break anything.  Before
> doing so validate that your wiring looks like the attached picture.
>
>
>
> ___
>
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> bottom of page at:
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>
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Re: Stus-List Problem with 2 new fuel gauges...long story

[Josh Muckley via CnC-List]

Excerpt from the following link:
http://www.doityourself.com/stry/how-does-an-analog-voltmeter-work

An analog voltmeter works by passing a current through a coil that is
suspended between two permanent magnets. This coil of wire is known as a
moving coil since it moves in relation to the permanent magnets when a
voltage is applied. When a voltage is applied and the voltage scale is
chosen, a resistor of known value is placed in series with the measurement
leads. This way Ohm's Law can be applied. The applied voltage through the
coil creates a magnetic field which acts against the permanent magnets that
the pointer pivot is placed between. This magnetic field causes a
corresponding deflection of the pointer. This pointer deflection will be in
direct proportion to the amount of voltage being applied to the moving coil
wrapping the pointer pivot. Once pointer oscillation has stopped, accurate
readings can be made.



So to summerize:  Yes Marek, basic analog meter movement is caused by
current flow through the meter coil.

I suppose in a a way that makes all anaolog coil meters "current" meters.
I referred to the fuel gage as a voltage meter so as to suggest that with
the meter completely removed from the boat a "voltage" applied across the
terminals from sense to ground or sense to vcc (+12v terminal) would cause
meter deflection.  In order to troubleshoot one might select a common 6v
lantern battery for this task.

Using the attached drawing as a referance and understanding that R2 is the
fuel level sender and "D" is the sender "sensing" terminal on the meter.  I
believe that inadvertently swapping the +12v and sense lines or swapping
the ground and +12v lines would cause the symptom of the fuel gage needle
pegging low.

To both our points, the attached picture suggests that the meter being used
is a voltage meter (Vg) and referances the current from points D to B (Ig)
as driving its movement.

Josh
On Apr 4, 2015 10:40 PM, "Marek Dziedzic via CnC-List" <
cnc-list@cnc-list.com> wrote:

>  Josh,
>
> This is certainly not sailing related, but if i remember it correctly,
> they are all really ammeters (the current flowing through them creates the
> magnetic field that moves the needle).
>
> Marek
>
>
>
> Josh Muckley via CnC-List wrote:
>
>  All analog meters are just measuring the "voltage drop" across a
> resistance.  The key is to have the appropriate voltage input +12v.  If the
> +12v and the sensing line were reversed then the "voltage drop" would be
> "negative" driving the needle to the empty peg.
>
> Josh
> On Apr 4, 2015 7:08 PM, "Wally Bryant via CnC-List" 
> wrote:
>
> I thought they were Ohm meters. Anyway, I just Googled it to make sure,
> and see a ton of pages on testing marine fuel sender resistance.
>
> Wal
>
> you wrote:
>
> I agree with your diagnosis.  It's gotta be reversed polarity...of the
> sense and gnd.  Fundamentally the fuel gages are just voltage meters.  They
> respond proportionally to the voltage drop across the variable resistance
> in the sender.  I would disconnect the leads and use an ohm meter to
> measure and validate the resistance of the senders.  Switching the polarity
> of the sense and gnd monetarily probably won't break anything.  Before
> doing so validate that your wiring looks like the attached picture.
>
>
>
> ___
>
> Email address:
> CnC-List@cnc-list.com
> To change your list preferences, including unsubscribing -- go to the
> bottom of page at:
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>
>
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>
>
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Re: Stus-List Problem with 2 new fuel gauges...long story

[Wally Bryant via CnC-List]

Okay, I'm grinning.  Now we have ammeters, voltmeters, and ohmmeters.  
Let's all just have a beer and admit that we don't really understand 
anything at all. 


I have noticed that when the house bank is low, my WEMA fuel gauge also 
reads low.  I've always wondered why, and figured that it had something 
to do with the voltage differential between positive and ground on the 
house bank somehow affecting the differential between the two on the 
starting bank.  The fuel sensor is definitely wired into the starting 
bank side of things, since it's involved with the whole engine thing.


I'm not a geek, but I suppose I was one once.  I have been drunk now for 
over two weeks, and some people say that there's a woman to blame.  Uh 
Oh, one must be in trouble when one gets Jimmy Buffet lyrics mixed up.


I gotta go fix dinner.

Wal


you wrote:

Josh,

This is certainly not sailing related, but if i remember it correctly, they are 
all really ammeters (the current flowing through them creates the magnetic 
field that moves the needle).

Marek


Josh Muckley via CnC-List wrote:

All analog meters are just measuring the "voltage drop" across a
resistance.  The key is to have the appropriate voltage input +12v.  If the
+12v and the sensing line were reversed then the "voltage drop" would be
"negative" driving the needle to the empty peg.

Josh
I wrote:


I thought they were Ohm meters. Anyway, I just Googled it to make sure,
and see a ton of pages on testing marine fuel sender resistance.

Wal




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Re: Stus-List Problem with 2 new fuel gauges...long story

[Robert Boyer via CnC-List]

When you connect the sensing wire to ground, the needle goes positive all the 
way as it should do but it does not register the fuel level.

I now believe that one gauge is working correctly because the needle moved 
slightly positive when energized--but the tank is completely empty.

The other gauge is hooked up the same way but I think the wires inside the tank 
sender is reversed, which makes the needle go in the wrong direction.  I remove 
the ground from the sender and reverse the sender polarity tomorrow.

Wal, would I also have to reverse the power supply polarity on the gauge to 
make it work properly?

Thanks!

Bob

Bob Boyer
S/V Rainy Days / Annapolis MD
1983 C&C Landfall 38 - Hull #230
email: dainyr...@icloud.com 
blog: dainyrays.blogspot.com

"There is nothing--absolutely nothing--half so much worth doing as simply 
messing about in boats."  --Kenneth Grahame

> On Apr 4, 2015, at 10:40 PM, Marek Dziedzic via CnC-List 
>  wrote:
> 
> Josh,
> 
> This is certainly not sailing related, but if i remember it correctly, they 
> are all really ammeters (the current flowing through them creates the 
> magnetic field that moves the needle).  
> 
> Marek
> 
> 
> 
> Josh Muckley via CnC-List wrote:
> 
> 
> All analog meters are just measuring the "voltage drop" across a resistance.  
> The key is to have the appropriate voltage input +12v.  If the +12v and the 
> sensing line were reversed then the "voltage drop" would be "negative" 
> driving the needle to the empty peg.
> 
> Josh
> 
> On Apr 4, 2015 7:08 PM, "Wally Bryant via CnC-List"  
> wrote:
> I thought they were Ohm meters. Anyway, I just Googled it to make sure, and 
> see a ton of pages on testing marine fuel sender resistance.
> 
> Wal
> 
> you wrote:
> I agree with your diagnosis.  It's gotta be reversed polarity...of the
> sense and gnd.  Fundamentally the fuel gages are just voltage meters.  They
> respond proportionally to the voltage drop across the variable resistance
> in the sender.  I would disconnect the leads and use an ohm meter to
> measure and validate the resistance of the senders.  Switching the polarity
> of the sense and gnd monetarily probably won't break anything.  Before
> doing so validate that your wiring looks like the attached picture.
> 
> 
> ___
> 
> Email address:
> CnC-List@cnc-list.com
> To change your list preferences, including unsubscribing -- go to the bottom 
> of page at:
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Re: Stus-List Problem with 2 new fuel gauges...long story

[Marek Dziedzic via CnC-List]

Josh,

This is certainly not sailing related, but if i remember it correctly, they are 
all really ammeters (the current flowing through them creates the magnetic 
field that moves the needle).

Marek


Josh Muckley via CnC-List wrote:

All analog meters are just measuring the "voltage drop" across a
resistance.  The key is to have the appropriate voltage input +12v.  If the
+12v and the sensing line were reversed then the "voltage drop" would be
"negative" driving the needle to the empty peg.

Josh
On Apr 4, 2015 7:08 PM, "Wally Bryant via CnC-List" 
wrote:

> I thought they were Ohm meters. Anyway, I just Googled it to make sure,
> and see a ton of pages on testing marine fuel sender resistance.
>
> Wal
>
> you wrote:
>
>> I agree with your diagnosis.  It's gotta be reversed polarity...of the
>> sense and gnd.  Fundamentally the fuel gages are just voltage meters.
>> They
>> respond proportionally to the voltage drop across the variable resistance
>> in the sender.  I would disconnect the leads and use an ohm meter to
>> measure and validate the resistance of the senders.  Switching the
>> polarity
>> of the sense and gnd monetarily probably won't break anything.  Before
>> doing so validate that your wiring looks like the attached picture.
>>
>
>
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Re: Stus-List Problem with 2 new fuel gauges...long story

[Russ & Melody via CnC-List]

It's okay Josh.

Wally is a geek, he knows. I think he was just entertaining himself. 
Maybe it gets lonely sometimes in Mexico after the sun goes down. :)


Cheers, Russ
east side, Vancouver Island

At 06:13 PM 04/04/2015, you wrote:

All analog meters are just measuring the "voltage drop" across a 
resistance.  The key is to have the appropriate voltage input 
+12v.  If the +12v and the sensing line were reversed then the 
"voltage drop" would be "negative" driving the needle to the empty peg.


Josh
On Apr 4, 2015 7:08 PM, "Wally Bryant via CnC-List" 
<cnc-list@cnc-list.com> wrote:
I thought they were Ohm meters. Anyway, I just Googled it to make 
sure, and see a ton of pages on testing marine fuel sender resistance.


Wal

you wrote:
I agree with your diagnosis.  It's gotta be reversed polarity...of the
sense and gnd.  Fundamentally the fuel gages are just voltage meters.  They
respond proportionally to the voltage drop across the variable resistance
in the sender.  I would disconnect the leads and use an ohm meter to
measure and validate the resistance of the senders.  Switching the polarity
of the sense and gnd monetarily probably won't break anything.  Before
doing so validate that your wiring looks like the attached picture.
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Re: Stus-List Problem with 2 new fuel gauges...long story

[Josh Muckley via CnC-List]

All analog meters are just measuring the "voltage drop" across a
resistance.  The key is to have the appropriate voltage input +12v.  If the
+12v and the sensing line were reversed then the "voltage drop" would be
"negative" driving the needle to the empty peg.

Josh
On Apr 4, 2015 7:08 PM, "Wally Bryant via CnC-List" 
wrote:

> I thought they were Ohm meters. Anyway, I just Googled it to make sure,
> and see a ton of pages on testing marine fuel sender resistance.
>
> Wal
>
> you wrote:
>
>> I agree with your diagnosis.  It's gotta be reversed polarity...of the
>> sense and gnd.  Fundamentally the fuel gages are just voltage meters.
>> They
>> respond proportionally to the voltage drop across the variable resistance
>> in the sender.  I would disconnect the leads and use an ohm meter to
>> measure and validate the resistance of the senders.  Switching the
>> polarity
>> of the sense and gnd monetarily probably won't break anything.  Before
>> doing so validate that your wiring looks like the attached picture.
>>
>
>
> ___
>
> Email address:
> CnC-List@cnc-list.com
> To change your list preferences, including unsubscribing -- go to the
> bottom of page at:
> http://cnc-list.com/mailman/listinfo/cnc-list_cnc-list.com
>
>
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Re: Stus-List Problem with 2 new fuel gauges...long story

[Wally Bryant via CnC-List]

I thought they were Ohm meters. Anyway, I just Googled it to make sure, 
and see a ton of pages on testing marine fuel sender resistance.


Wal

you wrote:

I agree with your diagnosis.  It's gotta be reversed polarity...of the
sense and gnd.  Fundamentally the fuel gages are just voltage meters.  They
respond proportionally to the voltage drop across the variable resistance
in the sender.  I would disconnect the leads and use an ohm meter to
measure and validate the resistance of the senders.  Switching the polarity
of the sense and gnd monetarily probably won't break anything.  Before
doing so validate that your wiring looks like the attached picture.



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Re: Stus-List Problem with 2 new fuel gauges...long story

[Josh Muckley via CnC-List]

I agree with your diagnosis.  It's gotta be reversed polarity...of the
sense and gnd.  Fundamentally the fuel gages are just voltage meters.  They
respond proportionally to the voltage drop across the variable resistance
in the sender.  I would disconnect the leads and use an ohm meter to
measure and validate the resistance of the senders.  Switching the polarity
of the sense and gnd monetarily probably won't break anything.  Before
doing so validate that your wiring looks like the attached picture.

Josh Muckley
S/V Sea Hawk
1989 C&C 37+
Solomons, MD
I'm sharing an electrical problem right now in the hope that someone here
on this list has had a similar problem and solved it...

Over the winter I added an auxiliary 19-gallon diesel tank under the nav
station seat.  I decided to buy 2 new fuel gauges, one for the new
auxiliary fuel tank and the other a replacement of a 30-year old fuel gauge
for the primary diesel tank.  Both (Sierra-brand) gauges are mounted in the
cockpit coaming on the port side with nice labels.

My 30-year old fuel gauge was working fine but it was mounted in the engine
panel and didn't match the color and style of the other gauges--this is
primarily why I replaced it.

I made a nice teak pad (located inside near the gauges) on which I mounted
terminals and bus bars to properly organize the new wiring for all the
gauges.  I completely wired up the new fuel gauges in accordance with the
instructions.  (I rewired so that I could get rid of a lot of old un-tinned
wire.)

When I turned on the ignition to check the gauges function, the needles on
both gauges moved to below empty.  This usually means an open circuit on
the sender side. I've thoroughly checked all the wiring and the gauges and
I can't find any problem with the wiring or the gauges.

I've checked the resistance across the sender on the new auxiliary tank and
it measures 230 ohms--since that tank is empty, the resistance sounds about
right.  The primary tank's sender is more difficult to access, so I
couldn't measure it.

Last night, I checked the tank's grounding by running some extra temporary
ground wires--no difference.

What's weird is that the problem is affecting both gauges the same way.
Any ideas as to what the problem may be?  Its almost like the polarity of
the power input is reversed, but it isn't.

Bob

Bob Boyer
S/V Rainy Days / Annapolis MD
1983 C&C Landfall 38 - Hull #230
email: dainyr...@icloud.com
blog: dainyrays.blogspot.com

"There is nothing--absolutely nothing--half so much worth doing as simply
messing about in boats."  --Kenneth Grahame

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Stus-List Problem with 2 new fuel gauges...long story

[Robert Boyer via CnC-List]

I'm sharing an electrical problem right now in the hope that someone here on 
this list has had a similar problem and solved it...

Over the winter I added an auxiliary 19-gallon diesel tank under the nav 
station seat.  I decided to buy 2 new fuel gauges, one for the new auxiliary 
fuel tank and the other a replacement of a 30-year old fuel gauge for the 
primary diesel tank.  Both (Sierra-brand) gauges are mounted in the cockpit 
coaming on the port side with nice labels.  

My 30-year old fuel gauge was working fine but it was mounted in the engine 
panel and didn't match the color and style of the other gauges--this is 
primarily why I replaced it.

I made a nice teak pad (located inside near the gauges) on which I mounted 
terminals and bus bars to properly organize the new wiring for all the gauges.  
I completely wired up the new fuel gauges in accordance with the instructions.  
(I rewired so that I could get rid of a lot of old un-tinned wire.)

When I turned on the ignition to check the gauges function, the needles on both 
gauges moved to below empty.  This usually means an open circuit on the sender 
side. I've thoroughly checked all the wiring and the gauges and I can't find 
any problem with the wiring or the gauges.

I've checked the resistance across the sender on the new auxiliary tank and it 
measures 230 ohms--since that tank is empty, the resistance sounds about right. 
 The primary tank's sender is more difficult to access, so I couldn't measure 
it.

Last night, I checked the tank's grounding by running some extra temporary 
ground wires--no difference.

What's weird is that the problem is affecting both gauges the same way.  Any 
ideas as to what the problem may be?  Its almost like the polarity of the power 
input is reversed, but it isn't.

Bob

Bob Boyer
S/V Rainy Days / Annapolis MD
1983 C&C Landfall 38 - Hull #230
email: dainyr...@icloud.com 
blog: dainyrays.blogspot.com

"There is nothing--absolutely nothing--half so much worth doing as simply 
messing about in boats."  --Kenneth Grahame___

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