Fuel gauge calibration

[Dermodad]

71 flat windshield superbeetle. My original sender unit was bad, but gauge itself would freely register full when sender unit bypassed. So I bought a new sending unit from JBugs, and an exciter while I was at it. Bench tested the new sending unit and it seemed good at both extremes (10/72 ohms). Once installed (with old exciter) it registers full at 10 gallons (great!),but drops precipitously so that at 3/4 full the gauge says 1/4. I have not trusted it enough to run to near empty so see what happens.


I've taken the sending unit out and played with again; and changed the exciter. No change in results. Installed, the sending unit reads about 25 olms with about 7.5 gallons on board.


I called JBugs techs and they suggested I needed to "calibrate my gauge to the new sending unit" by altering adjuster screws in the gauge itself. Most threads here just talk about bending the sending unit arms as adjustment. I don't see anything about changing the gauge calibration. I am a little wary of breaking into the gauge, although it doesn't look hard.


Anybody got any ideas on this?


Anybody got any insight into this problem?

[Tim Donahoe]

I think you got a bum sender.

I just read that someone else had problems with Jbug’s sender, which was a Dansk. They sent it back and got a Mexican one from Rock Auot. Then it worked fine.

You should NOT have to calibrate your gauge.

Tim
_________________
Let's do the Time Warp again!

Richard O'Brien

[390nellie]

I have the exact same problem. Purchased and installed a new tank, sending unit and vibrator from Jbugs. Fill the tank needle goes to full. When needle touches the first reserve line there is nearly 1/2 tank remaining.
I am reluctant to adjust the gauge. I'm afraid adjusting one end of the spectrum may only throw off the other.
If you do adjust the gauge please let us know the outcome.

[Blue69Baja]

Haw, I am right in the middle of this issue.

I have about 5 pages of tech notes related to the gauges currently being sold by everyone. Along with the Vibrator/regulator. I have 3 regulators and 4 gauges that I have purchased for testing.

As of now I am not ready to tell the whole tale but in a couple of weeks if I have time I will have some good information to post.

As of now I will say that calibrating the gauge is not an easy task and will not provide the results you will get. There are two adjustments for the gauge. The one you can see from the rear of the gauge is named Zero adjust and is a very fine adjustment. There is another one requires you to remove the plastic rear cover! It is named Range (by someone). That is the one that will move the needle quite a bit but it does not increase the travel of the needle. So if you say you want to move the needle more towards full then when the tank is empty it will read way above empty, probably around 1/4 to 1/2 tank hahahaa. If you do not have fine feel with your hands and a tool to work the teeth of the adjustment you should not attempt to adjust unless you are willing to purchase another meter in the case you damage the gauge.

Here is another problem: The non oem vibrator is not a vibrator circuit. It is a Zener 5.1 vdc regulator with a 5watt 12vdc lightbulb for a load. It does regulate the voltage pretty steady from 13vdc down to about 9vdc... The 5volts will vary a bit... .1- .3 vdc when the ignition is on, low battery charged battery, lights on and off.

I am waiting to pull a true vibrator out of my Baja to measure the actual performance.I also have a bud that has a couple laying around. OEM vibrators switch the 12vdc on and off to regulate the voltage of around 5.1 to the meter. I believe the actual means voltage will be higher than 5.1 vdc... The higher the voltage the wider the meter swing.. Problem is as the actual voltage goes up the current will increase... The question is how much current will the VERY FINE wire that is wrapped around the meters BI metal arm that bends from the heat generated by the current handle until it burns up? This is where I am at as of now.

I have opened one up to see how it is made and how it works.

Here is my Fuel Gauge project.

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69 Baja with a 1914...
72 Super 100% orig...W/ factory air... 56,000mi
Even the spare is original..

[TDCTDI]

Leave the gauge alone!

Get a one gallon gas can & fill it. Run the car until empty, pour the contents of the gas can into the tank, remove the sender & bend the float arm in the middle (so you’re not bending the arm inside the sender portion) & re-install the sender. Make adjustments until the gauge reads to the top of the reserve line.
_________________
Everybody born before 1975 has a story, good, bad, or indifferent, about a VW.


GOFUNDYOURSELF, quit asking everyone to do it for you!


An air cooled VW will make you a hoarder.


Do something, anything, to your project every day, and you will eventually complete it.

[Blue69Baja]

Here are a couple of pictures showing an OEM vibrator v/s the non OEM vibrator/regulator being sold by everyone.

Picture of the NON-OEM gauge. Note the light bulb. 12vdc 5 watt.

This is the back side of an OEM VDO vibrator.
Note the little black painted circle. That is a seal to lock the... WAIT for it!!!
A factory adjustment to calibrate the meter... It changes the on off of the bimetal lever for the contacts.
I have not had time to test a good OEM VDO vibrator to determine the actual average voltage... So hang tight and I should have some information..

This is the guts of an OEM vibrator. You can see the coil of wire that heats the bimetal arm... From reading it is suppose to switch on and off about 3 times a second... I have not verified that as a fact.

This picture shows the 2 adjustments for the needle.The top left one is the one that is not able to adjust without removing the plastic back of the meter.

Here you can see the fine wire of the bimetal lever.

_________________
69 Baja with a 1914...
72 Super 100% orig...W/ factory air... 56,000mi
Even the spare is original..

[Blue69Baja]

[Tim Donahoe]

I will never install another OEM vibrator. When they fail, they allow a full twelve volts into your gauge, which will fry your gauge (you’ll see the smoke when this happens). Besides, most OEM vibrators that still work have been doing so for decades. Sooner or later, that old sucker will fail. Not only can this burn out your gauge, it can also burn out the rheostat in your sender.

However, when the new “non-vibrator” vibrator fails, it simply stops the flow of voltage altogether, thus saving your ultra thin gauge wires and sender rheostat.

Be careful, however. There are good new-type vibrators out there. These have a small but obvious hump on the back. This type is more expensive than the cheapies which look pretty much the same—black plastic. But, from what I understand, they lack a zenor diode, so no hump in the back side.

It’s been awhile since I checked these out at any vendors, so for all I know, they may not even offer the cheapies, anymore.

Tim
_________________
Let's do the Time Warp again!

Richard O'Brien

[Blue69Baja]

[glutamodo]

[Blue69Baja]

Andy thanks for your input. Did not know that they went with the Zener diode regulator... Can you get a read on that Zener... 1nXXXX or whatever number style... I would like to know what voltage they were using if possible.

Jim.
_________________
69 Baja with a 1914...
72 Super 100% orig...W/ factory air... 56,000mi
Even the spare is original..

[glutamodo]

It's been a long time since I played with a German one - that photo above wat taken at the VW parts/service shop I used to work at, we had a couple of them mixed in with the vibrator style. (but I'm sitting about 170 miles away from there as I type this)

The old Haynes 1200 service manual - the original version that was 1200-centric, in its supplement chapters for years newer than 1966, had this to say - but no real values given. I'd have to dig into my boxes of stored books to access the diagrams mentioned here.

_________________
Andy T.


IMAGE NOTE: It has been noted that Chrome based browsers may have issues in displaying my vast image library, which use non-secure links and are on an FTP server. Images should still be viewable if the link is clicked though.
I do not know how to fix this. All I can say is it all works fine for me with what I use, Firefox.

[Blue69Baja]

Haw Andy, that would be the way to troubleshoot the current non OEM vibrator types currently avail. The diode shorts thus protecting the meter!
The bulb will get pretty warm then too.

Thanks for posting the document.

Jim
_________________
69 Baja with a 1914...
72 Super 100% orig...W/ factory air... 56,000mi
Even the spare is original..

[runamoc]

[Blue69Baja]

[glutamodo]

While I have a long history of mucking about with mechanical sending units, but as far as electrical ones, I've never gone and bent the arm. Never needed to. Okay, the gauge does have a factory-level adjustment, I have =very slightly= played with that before but not much. I've got my Baja (with a 1968 Speedometer, and later than that fuel gauge but I changed the faceplate out to keep with the 1968 motif- also, using a German replacement VDO tank unit) set up so I can trust the lower fuel level readings in a meaningful way.

A classic link for the fuel gauge: http://www.speedyjim.net/htm/fuel_ga.htm
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Andy T.


IMAGE NOTE: It has been noted that Chrome based browsers may have issues in displaying my vast image library, which use non-secure links and are on an FTP server. Images should still be viewable if the link is clicked though.
I do not know how to fix this. All I can say is it all works fine for me with what I use, Firefox.

[Blue69Baja]

[glutamodo]

I still dislike calling it "non-OEM" because, well, it was OEM. Hell, they both had VW part numbers! - 113957099 and 113957099A.

(I would rather call them "Vibrator" and "Zener diode" styles. )
_________________
Andy T.


IMAGE NOTE: It has been noted that Chrome based browsers may have issues in displaying my vast image library, which use non-secure links and are on an FTP server. Images should still be viewable if the link is clicked though.
I do not know how to fix this. All I can say is it all works fine for me with what I use, Firefox.

[Tim Donahoe]

Well, everybody knows what the vibrator is, but a zenor diode “style” doesn’t quite cut it. Zenor diode style ... what? It’s not a zenor style vibrator, because it doesn’t vibrate? So, do we call it a zenor style “gauge regulator”? Maybe that’s the ticket.

Tim
_________________
Let's do the Time Warp again!

Richard O'Brien

[glutamodo]

Well one is electro-mechanical and the other solid-state electronic.
_________________
Andy T.


IMAGE NOTE: It has been noted that Chrome based browsers may have issues in displaying my vast image library, which use non-secure links and are on an FTP server. Images should still be viewable if the link is clicked though.
I do not know how to fix this. All I can say is it all works fine for me with what I use, Firefox.