Fuel guage

Mike mcl99

Recruit
Joined
Aug 21, 2012
Messages
4
I have 12v to sending unit on tank, float is working & there is power to back of guage in dashboard. Is it safe to say guage needs replacing?
 

UncleWillie

Captain
Joined
Oct 18, 2011
Messages
3,995
Re: Fuel gauge

Re: Fuel gauge

Is it safe to say guage needs replacing?

Not at all.
The sender may be bad or the wiring is open.

Does the gauge read full or empty?
Is the tank full or empty?
What is the voltage on the TERMINAL (Not the Connector) on the Sender?
 

Mike mcl99

Recruit
Joined
Aug 21, 2012
Messages
4
Re: Fuel guage

Tank is half full. The guage on sending unit reads 1/2 that is mounted to top of tank
 

Mike mcl99

Recruit
Joined
Aug 21, 2012
Messages
4
Re: Fuel guage

Not at all.
The sender may be bad or the wiring is open.

Does the gauge read full or empty?
Is the tank full or empty?
What is the voltage on the TERMINAL (Not the Connector) on the Sender?

The sender has to pigtail wires, there is power in & out of sender
 

tswiczko

Master Chief Petty Officer
Joined
Feb 15, 2009
Messages
838
Re: Fuel guage

The sender has to pigtail wires, there is power in & out of sender
Does the gauge read full or empty and how much is in the tank

If it's reading full or way over the amount of fuel in the tank then the unit has a short and is sending a false reading. Which means you will have a signal out going to the gauge.

If there were signal (voltage) in and no signal out and there were fuel in the tank then you have an open circuit in the sending unit.

if you have signal out of the sending unit and the gauge reads empty doesn't necessarily mean you have a bad gauge.
You could have a bad ground to the gauge causing the circuit to not be complete.

Check that the gauge is grounded well before replacing it.
 

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,758
Re: Fuel guage

The sending unit does not get connected to +12 volts. It gets connected to the "S" terminal on the gauge. The metal shell of the sending unit gets grounded to the negative terminal of the battery or wherever you have a suitable ground connection. Those are the only two connections at the tank. At the gauge, +12 volts gets connected to the "I" terminal on the gauge. That wires comes from the "I" terminal on any other gauge or from the "A" terminal on the ignition switch. The "S" terminal we already discussed and the ground terminal gets connected to the ground terminal on any other gauge or wherever you find ground at the helm. If the gauge has an internal light the "L" terminal gets connected to the "L" terminal on any other gauge. If you use the search feature you will find dozens of posts about fuel gauge issues which always get the same responses and most have a diagram of the fuel gauge system.
 

UncleWillie

Captain
Joined
Oct 18, 2011
Messages
3,995
Re: Fuel gauge

Re: Fuel gauge

I failed to mention fuel gauge on dash doesn't work

The Gauge "reads" something. Full?, Empty?, Half?
Does it swing at all when you turn the ignition switch On/Off?

The sender has to pigtail wires, there is power in & out of sender

One wire will read Zero, the other should read 12 or less. What is the actual reading? (i.e. 11.7v)
That is NOT power, it is the gauge signal!
 
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