Low fuel warning light not working

[Ceejay 72]

I wrote previously about a sudden failure of my fuel level sensor whilst changing the fuel tank and found that yes, it was going to earth at all positions, so replaced it. So the fuel gauge now works again, BUT - the low level light doesn't.
I checked the new sender out of the tank and in the low position, the low level terminal switched to earth as it should.
I checked the voltage at each of the sensor live terminals and the level connector gave the correct 10.4 Volts, but the low level connector gave 11 Volts, not 12, which was a little puzzling.
Earthing the low level connector with the ignition on should illuminate the warning light, but it doesn't.
So my question is: if I have voltage at the low level connector, which has to pass through the warning bulb to get there, why doesn't the bulb light when the connector is earthed?

Chris

[dasadrew]

bulb blown?

[Ceejay 72]

If it was blown, would there be voltage at the low level connector?

[Lingen]

Chris.
The volt meter you are using will only take a minute current to operate it. You are correct in saying that there must be something passing through the bulb to work the meter, but perhaps not enough to illuminate a bulb. I would try fitting another one to see if it works. If not, then a further search will be necessary.

[Ceejay 72]

Thanks for the info - oh well, off with the instrument panel again!

Chris

[jakesmig]

Could it be that the float of the sender is sitting too low in the tank and is resting on the bottom of the tank before it reaches the earthing point in the rheostat?

John.

[wilf]

To check the bulb, simply earth the relevant wire at the sender. The power supply for that warning light does not come from the voltage stabiliser, it is a direct 12V from the battery via the ignition switch. So, if the bulb was OK, you should have 12V or battery voltage at the tank end.

BTW, should you need a new bulb, the ones you can buy now are ever so slightly too big for the copper holders in the warning light cluster, you will have to open that up a fraction.

[DZP]

If the bulb is OK and you still do not get it to light when you earth the wire at the sender, then you probably have a poor connection in the 12v feed somewhere, preventing current flow and creating the slight voltage drop you can see.
The right-hand rear harness connector in the drivers footwell is a good place to check.
Den

[StagJonno]

Agree with Den, examine the connector in the drivers footwell (note, the wiring diagram is indicating another connector, possibly behind the dash, as well). The Fuel Low circuit works at battery voltage (not from the stabiliser), so 11V is pointing to a discharged battery.

[Ceejay 72]

The battery is fine. The light does not come on when I earth the connector at the sender, so I think Lingen's post 4 is possibly the right answer. I'll check the bulb first before going into the loom!
Chris