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" <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.
> 
> 
> _______________________________________________
> 
> 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
> 
> _______________________________________________
> 
> 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
> 
_______________________________________________

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

Reply via email to