Yet another fuel gauge thread (Yes I searched)

[bmartinek]

Thanks for humoring me and my Fuel gauge woes by reading this post.

I read the Atwell link as well:
http://www.nls.net/mp/volks/htm/fuel_ga.htm

and this one too:
http://type2.com/library/misc/vwggauge.htm

Right now I have the following situation on a '71 Deluxe:

I have tested the sender and it seems good. It had 75 ohms for empty and about 12 ohms for full. this seems to work. atleast according to this guide:
http://www.midsouthvw.com/TechTips/tech_tip_FuelGauge.htm

I checked my ohm reading from the brown wire to the gauge and to a ground and I am getting about 69 ohms. This seems correct since I have about 1/3 - 1/4 full tank.

After checking the black wire and a good ground I am getting a reading of about 11.4 volts. Its been a about 2 weeks since I have driven my bus.

Now when I switch on the ignition I get a full tank, .

Very frustrated and confused, any help would be greatly appreciated.

[DJ S.]

same freaking problem

[77VWBusDude]

Swap the wires?






Nah, I have no freakin' clue
_________________
'77 Bus auto EFI(stock)

[Mr. Loaf]

Were you reading right a few weeks ago? Did you pull your sender unit and look at your gauge after you reinstalled it? I'm thinking if you didn;t do this you might have a short at the sender. In other words, your sender seal is not isolating the sender from the tank.
_________________
Never drive faster than your Angel can fly
$24,100 was too hard to resist.................

[busdaddy]

Does it still read full with the wire off at the sender?
Could also be the gauge terminal shorting in the cluster housing.
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[bmartinek]

I think Busdaddy might be the closest!

My gauge has never read and so I have sought to fix it.

I don't think the sender shorting otherwise my ohm value at the gauge lead would have been much lower, not the expected 60 - 70 range.

I will try those checks Saturday I think. I am sooooo excited to finally have a working fuel gauge!.

Thanks Busdaddy, Mr. Loaf and good luck DJ. S

[DJ S.]

tell me what you have done once you fix it

[bmartinek]

I ran the tests today and am still not sure of the solution:

Results:

[onion456]

just thought i would throw out there; be careful when testing and messing around with the electronics. the gauge has a vibrator in the circuit that regulates the 12v, so that the fuel gauge will be stable regardless of fluctuations in voltage. one other thing the vibrator does is limit the current flowing through the gauge and sender. i believe the following pic is what happens when you bypass the vibrator and apply battery voltage directly to the gauge. there would be no current regulation, so max current flowing through these tiny resistance coil wires = burnt sender.

this is my sender- notice the metal housing- nice and shiny, this was a brand spanking new sender. what are they now, like $50? just make sure any voltage you send down the sender line is regulated, i.e. from the vibrator only.

a little scary too, this sender was installed in the tank at the time when it cooked.

after replacing yet another sender, and testing the circuit a little more carefully, i found the vibrator to be at fault. it would read good sometimes... but then dip in voltage for no apparent reason, and my gauge would move all over the place, mostly to empty and beyond. i had 3 vibrators to work with and they were all bad, including one brand new one. i finally gave up on the whole thing and bought an aftermarket fuel gauge that has its own vibrator built in; it aint perfect but it is stable. i added a 1k pot in the circuit and ran the bus till it ran out of gas, then dialed in empty so it is right on the E. at full, the gauge only reads 1/2 tank, but E is E and thats what matters to me. the gauge itself cost less than a new vibrator for the original circuit. im more or less happy with it. yeah im a little bummed that i couldnt get the original to work, but i tried and tried and tried some more, im tired of throwing money at it and i need a working fuel gauge.
_________________
'76 Sage Green Westy 2.0 FI
'76 Creamsicle 7-passenger 2.0 CS FI
'85 Tan Westy

[bmartinek]

Hey Onion,

That looks like a serious drag about the senders.

Unless the previous owner did somehting really weird (never rule that out) my '71 should have a dual coil gauge setup that doesn't use a vibrator like the later model bays.

thanks for the thought though.

[bmartinek]

Anybody?

Bueller?

[Jody '71]

Checking the diagram, and I may be way off here, but the sender wire connects at the T6 cable connector, then forward to the fuel gauge. Is there a possibility that current may be getting thwarted at the T6?

Viewing the first link, and this may not have anything to do with your problems, but it's mentioned that intermittent function of the gauge/ needle itself may be due to loose connections on the back of the gauge which are held down by the two hex nuts, or poor fuse contact.

I have yet to diagnose my '71's fuel gauge wackiness. It does this:

Full tank: needle is fine

Half tank: still fine

Between Half and 1/4 tank: needle gets bouncy, stops, then starts
getting bouncy again, then stops, and can't decide (or I can't)
if it's reading the proper fuel level any longer.

'Till I get this figured out, I keep it at least half way full of fuel. I think and hope it may just be the connections on the back of the gauge itself. Always consider the wires themselves that connect everything. I had a previous problem with the VR wire that went up to the dash. It had roached out and I never found the location. I ran a seperate wire and that fixed everything.
_________________
'66 Beetle
2011 Hyundai Elantra Touring

[bmartinek]

Hey Jody,

Thanks for the reply. It sould like out problem may be the bottom part of your sender going bad like an intermittent connection.

I do like your idea of running a whole new lead to the gauge and seeing the results. Wow thats a long wire! Mi gauge has just been pegged to full. No changes.

[busdaddy]

If you can't get your hands on another sender to at least hook up out of the tank and try then the wire is a great idea. You must have a sender access hatch so running it through the bus wouldn't be too long for a temporary test.

Jody, you described the gauge in my 71 perfectly, I've always attributed it to a bad spot in the sender, mine smooths back out under 1/4 and I figure if it's bouncing there's lots of fuel moving it so I'm fine.
_________________
Rust NEVER sleeps and stock never goes out of style.

Please don't PM technical questions, ask your problem in public so everyone can play along. If you think it's too stupid post it here
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[VWDruid]

Any one have a diagram of the way its hooked up inside of the gauge cluster?

mine just started acting up after filling it up with 11 gl, flinched a few times then went to 0.

I'm getting a reading of 3 to 4 volts coming out of the cluster.
_________________
70 Westy, 2027cc "dual DRLA 40 m140 i55 wjdoc a165 p33 v30 "w100 straight cut 040 polished heads 1.25 rockers 1.5 A1sidewinder supertrapp muffler trans 091 coil SUM-850500 CDI universal svda Pertronix
http://www.storyofstuff.com/
It's not the straight cut gears It's the T.A.R.D.I.S. engine.
wanted Chameleon Circuit

[Jody '71]

Diagram available above in Technical, click on wiring, select your year model, being sure you're in Type 2 first.
_________________
'66 Beetle
2011 Hyundai Elantra Touring

[busdaddy]

[VWDruid]

I have the Bentley I'm talking about the guts, I see how the black wire is the power in to the vibrator? brown is the ground to the gas tank.

brown wire to gas tank "G1" Busdaddy

http://www.thesamba.com/vw/archives/info/wiring/baybus_70a.jpg
_________________
70 Westy, 2027cc "dual DRLA 40 m140 i55 wjdoc a165 p33 v30 "w100 straight cut 040 polished heads 1.25 rockers 1.5 A1sidewinder supertrapp muffler trans 091 coil SUM-850500 CDI universal svda Pertronix
http://www.storyofstuff.com/
It's not the straight cut gears It's the T.A.R.D.I.S. engine.
wanted Chameleon Circuit

[busdaddy]

A 70 doesn't use a vibrator to regulate voltage at the gauge, different system.
If you are getting voltage at the brown sender wire the gauge is likely good, can't say the same for the sender though, what happens if you ground the terminal the brown wire goes to?
_________________
Rust NEVER sleeps and stock never goes out of style.

Please don't PM technical questions, ask your problem in public so everyone can play along. If you think it's too stupid post it here
Stop dead photo links! Post your photos to The Samba Gallery!

Слава Україні!

[VWDruid]

go's to full.

so I have a bad ground or some junk hanging up the sending unit.

the tank was removed cleaned and sealed with red kote 6 or so months ago.
no ode colored bits in the fuel filter.

so if the 3 volts from the gauge is fine and the gauge reads full when grounded has to be the sending unit.

i did test the wire at the back of the bus, so it is getting power there.
_________________
70 Westy, 2027cc "dual DRLA 40 m140 i55 wjdoc a165 p33 v30 "w100 straight cut 040 polished heads 1.25 rockers 1.5 A1sidewinder supertrapp muffler trans 091 coil SUM-850500 CDI universal svda Pertronix
http://www.storyofstuff.com/
It's not the straight cut gears It's the T.A.R.D.I.S. engine.
wanted Chameleon Circuit