I installed a NEW Toyota fuel sending unit 2 weeks ago.
(honestly wasn't that difficult with near empty tank)
Fuel gauge works perfectly now

NOW: The low fuel light just barely glows always...you can't even see it during the day unless you look very carefully, it's so faint.

My guy @ Toyota suggested a bad ground (tank is grounded @ the pump housing only) so I added a great ground to a screw on the pump housing this weekend.

Zero change.

Ideas?
Defective unit?
Maybe junk in the tank?
Bad wire connection somewhere?
Think I need another ground wire directly to the sending unit housing?

Thanks, all!

 

I wonder if it isnt in your speedometer assembly. Is there a crack letting light in from another source or from one of the other bulbs? Is it bright at night when the headlights are on?

I am fairly sure thew Fuel Light is an option. Does the replacement have a 3 wire plug? The ones without the Low Fuel Light is only a 2 wire plug.

Here is the difference. Round plugs are for the 86 and older but you can see the number of wires and the differences of the option on the Sending Unit. The Bulb at the bottom of the unit is what triggers the light. Just because you install the 3 wire unit, it has to be wired in the main harness.
Low Level Light Option and plug differences.

 

Thanks, Terry.
The sensor was purchased new from Toyota based on the VIN.
And, yes, it was the 3-prong with the green outer just has you have shown...matched the one I pulled out.
(The fuel gauge was completely dead when I bought the truck. Works perfect now.)

I did think about maybe it was light from a neighboring bulb, but I can see the glow when all lights are off...even just with the key to "on" regardless of whether the engine is running or not.

 

For sure a bad ground but the fun will be figuring out just where it is from.

Poor ground to the fuel gauge grounding back through the low fuel light??

Since this just started when you installed this.

Connector was clean with no corrosion on the truck harness??

 

Thanks, Wyoming. Gives me so good ideas to check out this weekend. This truck does have a fair amount of corrosion everywhere, unfortunately.
Maybe I'll run a ground wire directly to the sending unit, too...just to cover all bases.

I seem to recall seeing a writeup to test the connection somewhere but can't find it again.

I'll keep y'all posted.