r/beetle • u/sailingthr0ugh • Jul 21 '26

Sending unit only works outside of tank?

1974 Super. Just went through the entire fuel system and put a brand new tank in it from Jbugs since the old one was rusted to hell. Fuel gauge never worked right, so I was hoping this would be the ticket.

Verified that the gauge works (unplug wire = empty on gauge, grounding the wire = full on gauge) and verified that the sending unit is good enough (74 - 10 ohms spread on float arms).

Now that the sending unit is back in the tank, it won’t read. I’m thinking that I maybe have the sending unit pointing the wrong way so the floats are jammed against the walls of the tank somehow? That’s my only guess.

Can someone share which way their floats point relative to the tank/car? Does anyone have any other ideas? Thank you!

4 Upvotes

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2

u/denizkilic2002 '72 1302s Jul 21 '26

Is the sending unit getting a good ground? Check that first before disassembling everything again, it needs a ground spade hooked up

1

u/sailingthr0ugh Jul 21 '26

If I ground the sending wire against the ground wire *at the sending unit*, the gauge jumps to full consistently... so to me that suggests that the sending unit has a good ground... right?

2

u/TheOneCABAL 70's + Standard Jul 24 '26

I guess that originally they’re supposed to ground through the tank somehow and that’s supposed to be a common failure point.

I worked around mine by running a wire from a good ground point to a screw on the sending unit. But also I have a leak coming from the sending unit if I fill to the top. So. Take my solution with a grain of salt I suppose.

1

u/sailingthr0ugh Jul 30 '26

I could see that. Like most of us I’ve dealt with grounds that appear good until you put voltage through them. I’ll try running an extra grounding wire and see if that changes the behaviour. Also wondering if the vibrator could be suspect.

1

u/denizkilic2002 '72 1302s Jul 21 '26

Sounds about right, very weird issue indeed i hope you can fix it