1990 Range Rover fuel gauge problem

Hi all,
1990 2.5 VM with the following problem: fuel reserve warning light always on regardless of the liters of fuel in the tank
already replaced the fuel tank sender unit but the problem remained
at this point all that remains is to replace the RTC6600 gauge fuel or is there some other component that could give this problem ?
thank you
Giacomo

Checking along the wiring from the sender plug? Could a wire have rubbed through causing an earth somewhere? 33yrs is a long time to rub against something!!
Failing that take the bloody bulb out and keep a good eye on it

Hi Mark and thank you for answer
I still have to check the wiring....
Giacomo

But how do I know which of the 2 black wires is that of the reserve light ?
thank you
Giacomo

I very much doubt it's the gauge & light.

Check the connector plugs on the wires near the tank.
May be corrosion issues in the connectors or penetration & corrosion in the wires themselves.

Had that with the fuel pump live feed on my petrol '86 3.5EFi - down to a couple of strands inside the sheathing about an inch up the main loom from the round connector plug.
Enough to give battery volts on a digital multimeter but not to carry enough load to run the pump.
Located by a test bulb with a crocodile clip on one lead & a pin soldered to the other. Croc clip to a good clean earth, ignition on, afm flap propped open to energise the wire & work along the wire pushing the pin through the insulation until the bulb lit.

Can't help with which wire on yours is which though.
Wiring diagram required.
I don't know if it works as an earth & puts the bulb when the tank unit gets to a certain level on so worth using a multimeter to see which wires are live.
If it is an earth then use the pin & clip method. Clip to good earth - I take a long lead to battery earth terminal - and use the pin to the plugs & then along the wire until the low fuel warning light goes out.
You could probably do the same by connecting a multimeter set to continuity to the terminal of the wire at the gauge (take it off the gauge) then start at the tank end & work your way back up the connectors & loom until the meter shows you have continuity in that wire.

giacomo.m said:

But how do I know which of the 2 black wires is that of the reserve light ?
thank you
GiacomoView attachment 292884

Click to expand...

Looking at the picture, there is a third pin at the bottom of the tank wire fitting. Have you tried putting the plug with the two black wires in it on the bottom pin/spade.

Already tried but does not give the reading....
the right pins of the plug are these
Giacomo

And you've swapped them around in the different configurations?
Is the replacement sender the same as the old one

My 1995 copy of RAVE shows the following, but no idea if yours is the same. Cannot find anything about sender unit wiring yet.

Mark Piercy said:

And you've swapped them around in the different configurations?
Is the replacement sender the same as the old one

Click to expand...

replacement sender the same : PRC8823

pwood999 said:

My 1995 copy of RAVE shows the following, but no idea if yours is the same. Cannot find anything about sender unit wiring yet.

View attachment 292904

View attachment 292905

Click to expand...

thank you, but unfortunately it is not the same, 1990 is different