Fuel Sending Unit/Gas Gauge Issue

[1madmanx]

On my drive into work this morning in the Thing my 1/2 tank of gas (registered on the gauge when I left) was registering full when I arrived work. While I know my coffee hadn't kicked in yet, I'm pretty sure I didn't stop and fill the tank

I pulled the wire off the sending unit and the gauge fell to empty. I put the wire back on and the gauge moved to full. I banged on the top of the tank thinking the float might be stuck, but no change.

Where should I start? Pull the sender and verify that the float isn't stuck? Replace the sender? By the way, $75 seems a little steep from one of the "specialty" shops. What year is this sender equivalent with on a Beetle? I have a '74 Thing.

Thanks for any pointers.
Bud
_________________
Bud (1Madmanx)
Wilmington, NC
'68 Meyers Manx Dune Buggy M1996F826S
'66 Kombi Bus
'73 Thing
Visit my Galleries:
https://manxclub.com/forum/app.php/gallery/album/44

[vwwestyman]

First thing to do would be to pull the sender from the tank and inspect closely for operation as well as broken wires and such.

They are fairly easy to fix up with a little work, and very easy to get to on a Thing!

Here is a Bus sender (very, very similar) that I took apart. I cleaned up all the contacts of the float lever and all that, warmed the board that the resistance wire is wrapped on and flexed it towards the wiper arm, and on this one had to repair a broken contact wire.

I did basically the same operation to the sender on my Thing when I got it up and running.

_________________
Dave Cook

President, Wild Westerner Club

1978 Champagne Edition Westy, repowered to '97 Jetta TDI
1973 Wild Westerner
My Thing

[1madmanx]

Thanks Dave. I've never taken one apart before. Does look pretty simple. I'll give that a try tonight.

Bud
_________________
Bud (1Madmanx)
Wilmington, NC
'68 Meyers Manx Dune Buggy M1996F826S
'66 Kombi Bus
'73 Thing
Visit my Galleries:
https://manxclub.com/forum/app.php/gallery/album/44

[vwwestyman]

Good luck!

There are just little tabs that hold the float lever cover in place, so just bend them back to open it up.

Then take a little sandpaper and clean up everything where one part is supposed to contact another.

If your resistive wire is broken, I believe it can be replace inexpensively. I've found a couple threads in the Bay forum outlining replacing the wire and where to find it.
_________________
Dave Cook

President, Wild Westerner Club

1978 Champagne Edition Westy, repowered to '97 Jetta TDI
1973 Wild Westerner
My Thing

[1madmanx]

Interesting (at least to me) update: I filled the tank at lunch today to make sure I don't run out of gas until the issue is resolved. Part of me wanted to see if by pushing the float all the way up, I could "shock" the sender back to it's senses. Initially nothing happened (still read completely full), but after driving down the road a bit the fuel gauge went to empty (actually out of sight empty). Almost as if the wire was pulled off the sender (which it wasn't).

We'll see what we shall see when I pull the sender out.

Thanks.
_________________
Bud (1Madmanx)
Wilmington, NC
'68 Meyers Manx Dune Buggy M1996F826S
'66 Kombi Bus
'73 Thing
Visit my Galleries:
https://manxclub.com/forum/app.php/gallery/album/44

[vwwestyman]

Look closely at the wires too.

If there is a chafed part, it may have grounded out causing the full reading. If it broke all the way, you may have it occasionally grounding out, and other times no connection at all.
_________________
Dave Cook

President, Wild Westerner Club

1978 Champagne Edition Westy, repowered to '97 Jetta TDI
1973 Wild Westerner
My Thing

[lqqkatjon]

I purchased the sender from Thingparts.com, was reasonably priced.

from my understanding, is it is the same as a bug/beetle sender, without the cover over the terminals on the top. I understand The more expensive Thing shop sender is just like the OEM with the cover over the terminal on top.

[1madmanx]

[1madmanx]

[mondshine]

I noticed that the wire coils are not evenly spaced.
Maybe that's why I can go about 140 miles before my gauge reads 1/2, than 60 more miles to empty

[vwwestyman]

They aren't supposed to be evenly spaced. That's part of how the variable resistance is done.
_________________
Dave Cook

President, Wild Westerner Club

1978 Champagne Edition Westy, repowered to '97 Jetta TDI
1973 Wild Westerner
My Thing

[74 Thing]

I would like to understand what contacts were cleaned and what piece was pushed over in reference to the photos.

Thanks for the help.

[vwwestyman]

Hope this helps. Be gentle with cleaning up the contact area of the small wire that is wrapped around the "circuit board."

Not pictured in this pic is a little spring that goes with the wiper arm pivot. I also cleaned up the ends of the spring.
_________________
Dave Cook

President, Wild Westerner Club

1978 Champagne Edition Westy, repowered to '97 Jetta TDI
1973 Wild Westerner
My Thing

[helowrench]

http://www.midsouthvw.com/TechTips/tech_tip_FuelGauge.htm

this applies to your system as well.

Rob
_________________
Current VWs:
70 bug vert for wifey
73Thing bucket o rust
73 914 1.7
12 Passat 2.5 Highway cruiser

[1madmanx]

The weather has finally cooperated and the brown truck has delivered my parts so I was able to fix my sender/gauge issue. Unfortunately the fix wasn't the obvious one!

Best I can tell there are three components to the fuel gauge system: 1) sending unit in the tank, 2) the vibrator on the back of the speedo that the sending unit wire goes to, and 3) the gauge itself. Being the methodical person I am, I started by replacing #1. While part of this thread talked about repairing a sending unit, I didn't find anything wrong with mine and it still didn't work. New one it was. FAIL! New sending unit didn't fix the problem either.

On to #2. I replaced the vibrator with a new one. FAIL! New vibrator had no effect.

Last, but not least the gauge itself #3. I replaced the gauge in the speedo and DING DING DING, we have a winner! Who knew?

I've never heard of a gauge going bad and since I've never really looked at one before, I have no clue what's wrong with the old one.

Moral of the story, it's always the last place you look

Thanks to all who contributed to this thread. I learned a lot.

Bud
_________________
Bud (1Madmanx)
Wilmington, NC
'68 Meyers Manx Dune Buggy M1996F826S
'66 Kombi Bus
'73 Thing
Visit my Galleries:
https://manxclub.com/forum/app.php/gallery/album/44

[vwwestyman]

If you still have the odds gauge, look carefully inside. You'll see a very thin wire attached to the needle. If it breaks, the gauge won't work.

I had something hooked up wrong on a different bus and burned that wire up pretty quick, since the vibrator was accidentally bypassed, sending full voltage to the gauge.
_________________
Dave Cook

President, Wild Westerner Club

1978 Champagne Edition Westy, repowered to '97 Jetta TDI
1973 Wild Westerner
My Thing

[1madmanx]

[GI Joe]