Low gas tank warning light permanently on

[Stevehose]

I replaced all gauge bulbs over the weekend to the 4w variety and I noticed that after doing so the white T light is on when the ignition is on.

I disconnected the terminals at the sender unit and it still stays on.

There seem to be 2 wires attached to the socket. According to the wiring diagram the brown/black goes to the sender and the green/white goes to the fuse box and on to ignition switch?

Any ideas as to troubleshoot? Bad socket maybe?

 

[Arde]

My guess is that the sender side goes to a normally open switch to ground. The fuse side would be the power side for the bulb. You obviously have power at the light so troubleshooting would be about finding why the path to ground is closed.
I did not even know we had such a light. I assume the sender side uses the same float mechanism as the fuel level sender with a different switch for the light. That switch may be dead or you may have a short downstream of the sender. I would unplug the sender line for troubleshooting just for safety.

 

[lloyd]

http://www.e9coupe.com/forum/showthread.php?t=1390

http://www.e9coupe.com/forum/showpost.php?p=58265&postcount=4

 

[Stevehose]

Thanks that helps with the wiring but the gauge works fine and the the light stays on even with both wires disconnected at the sending unit, so my guess, given Arde's theory that the power comes from the ignition switch to the bulb then onward, is that the short to ground would be in the bulb holder because when I insert it back into the gauge the light goes on.

Will see what I can see but it's not easy working up in there.

http://www.e9coupe.com/forum/showthread.php?t=1390

http://www.e9coupe.com/forum/showpost.php?p=58265&postcount=4

 

[sfdon]

Disco the green/white from power or remove bulb- and then pin out for ground at brown/black at sender with sender disconnected.
If you see continuity you have a dead short to ground.

 

[adawil2002]

Here's my wise guy comment, just remove the bulb since the gas gauge works.

 

[Stevehose]

Andrew, that would be too easy and not lead to frustration, sore back, etc. But hopefully salvation is near:

The problem appears to be a broken socket. Compared to the oil light socket in the picture, the oil light is encased in plastic to prevent it grounding on the gauge housing, the tank light one is missing the sides (the top part is still there). The oil light works when it is not in the housing, I suspect the tank light is the same so I will find an appropriate plastic sleeve and make an insulator. This will keep it from grounding at the housing and allow it to ground back at the tank after the low fuel switch is tripped.

Thanks for the tips I will update when I can test it all.

Here's my wise guy comment, just remove the bulb since the gas gauge works.

 

[rsporsche]

Steve,

i just sent you an email ... got a box ready if you need it.

 

[Stevehose]

Thanks very much for your offer, I've confirmed that the light uninstalled in the gauge lights up when I jump the sender unit. I just need to fabricate an insulator.

Steve,

i just sent you an email ... got a box ready if you need it.

 

[bluecoupe30!]

gas tank light

Congrats Stevehose,
You are merciless at leading us through all manner of E9 foibles. A true leader! What a collection of issues and diagnostic step by step. We all owe you a debt of gratitude. Can't wait for my gas tank light to stay on! Seriously, I admire your tenacity and your contributions to this site are invaluable. Thank you. Mike

 

[Stevehose]

That's very kind but it's the other members here that get me out of the situations I find myself in. This forum makes owning these cars much more manageable and I have made some good friends along the way. I just post the pictures hoping to pass something useful along.

Congrats Stevehose,
You are merciless at leading us through all manner of E9 foibles. A true leader! What a collection of issues and diagnostic step by step. We all owe you a debt of gratitude. Can't wait for my gas tank light to stay on! Seriously, I admire your tenacity and your contributions to this site are invaluable. Thank you. Mike

 

[Arde]

Good outcome, no need to mess up with the tank, just a socket condom and problem fixed.

Another win for YHS, aka the armchair car electrician.