fuel gauge D2

**Outback 1** · 11th January 2015, 05:41 PM

they are a float on a wire but the most likely reason for your issue is the contact arm not touching or the slide it runs against is badly worn

**PeterM** · 11th January 2015, 06:33 PM

The gauge reads through its full arc without issue, just that it is incorrect.

Looks like a bit of wire bending is in my future ...

**Geoff** · 14th January 2015, 02:33 PM

Ok, checked the sender unit on the pump and it is all attached and the connections are good.

I plugged the sender in while it was out and tried moving the arm to see if the gauge moved but to no avail.

Can I short the wires at the connector to see if the problem is in the sender unit?

**Pippin** · 14th January 2015, 05:24 PM

Hi Geoff,
Sorry to hear that it was not caused by a detached sender. "The sender unit comprises of a rotary potentiometer supplied with a voltage of 5.0V from the instrument pack. The output voltage from the potentiometer varies according to the resistance through the potentiometer in relation to the fuel level. The output voltage is connected to the fuel gauge in the instrument pack. The fuel gauge receives a battery voltage input and this is compared with the output voltage of the potentiometer. The difference between the voltages determines the deflection of the fuel gauge pointer." This is from the manual. You should check with a multimeter that you have the 5V at the sender and a varying voltage from it's output when you move the float arm. It may be that the sender is faulty, do this test first and we can take it from there.
Nick

**Pippin** · 14th January 2015, 06:05 PM

Geoff,

If you do not have access to a multimeter shorting the sender wires will show a full tank on the gauge but be very careful if you do this.

Nick

**Outback 1** · 14th January 2015, 07:18 PM

when you get the time I have a working one here we can plug into it

**Geoff** · 17th January 2015, 09:53 AM

ok, some results. I think I will take you up on your offer Ken.

1. disconnected the electrical plug at the sender/pump unit, put the multimeter across the sender pins = open circuit (with tank 3/4 full)

2. shorted the pins = no movement on the fuel gauge.

3. shorted the pins at the under bonnet fuse box and when I turned on the ignition on, the gauge showed full then dropped back to empty

4. shorted the pins on the other side of the connector at the fuse box and measured continuity at the sender unit plug = 0.6 ohms resistance so the wires are intact.

5. checked continuity between sender wires and ground = pink wire is ground

6. tried again shorting the pins at the sender unit, this time with a paperclip (like in step 2) and when I turned on the ignition on, the gauge showed full then dropped back to empty

this leads me to believe the sender is faulty

what do you think, is the pink wire supposed to be ground?

cheers

**sierrafery** · 17th January 2015, 10:47 AM

Originally Posted by Geoff

...what do you think, is the pink wire supposed to be ground?

cheers

Yes it is

**Pippin** · 17th January 2015, 11:20 AM

Originally Posted by Pippin

Hi Geoff,
Sorry to hear that it was not caused by a detached sender. "The sender unit comprises of a rotary potentiometer supplied with a voltage of 5.0V from the instrument pack. The output voltage from the potentiometer varies according to the resistance through the potentiometer in relation to the fuel level. The output voltage is connected to the fuel gauge in the instrument pack. The fuel gauge receives a battery voltage input and this is compared with the output voltage of the potentiometer. The difference between the voltages determines the deflection of the fuel gauge pointer." This is from the manual. You should check with a multimeter that you have the 5V at the sender and a varying voltage from it's output when you move the float arm. It may be that the sender is faulty, do this test first and we can take it from there.
Nick

Have you checked the voltage delivered to the sender unit as above and checked for any output?

**sierrafery** · 17th January 2015, 12:51 PM

Actually the explanation from RAVE in this case is not the best as the sender's variable resistance is sensed by the gauge on the earth path as the sender's one side is to earth(pink/black wire) and the other is connected to the gauge which gets the supply from the instrument pack, a bit contradictory i know but the diagram confirms the description of the fuel gauge from the instruments section:

"The signal input for the fuel gauge is from the tank sender unit, it is a variable voltage signal proportional to the level
of fuel in the tank. The instrument pack provides the power via fuse 27 to the fuel gauge, then from the gauge on to
the fuel tank sender unit. The earth path return circuit of the sender unit is connected to the instrument pack.

IMO the answer lies in the following statement

Originally Posted by Geoff

1. disconnected the electrical plug at the sender/pump unit, put the multimeter across the sender pins = open circuit (with tank 3/4 full)

which means the pump must come out and see if the sender(potentiometer) is not interrupted at a joint or something cos at 3/4 tank you must get around 36 Ohm reading(see attachment)... there vare senders as spare on the market part number YAD500040

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