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Wed Jun 25, 2014 5:31 am

I got a second hand fuel gauge to supplement my stock one, and i did the following checks to see if it was working:

12v to plus terminal, G terminal to ground and needle moved up a little to zero.
12v to plus terminal, upside down T terminal to ground and needle shot up to full.

So gauge is good.

I then wire it up to the sender thus:

12v keyed to plus terminal
Black wire from sender to G terminal (other brown one goes to ground)
Wire to ground from upside down T terminal.

I turn the key on and the needle moves up a teeny bit to just before zero, despite the stock gauge showing a full tank, which is correct.

What can I be doing wrong?
Thanks in advance.

Wed Jun 25, 2014 10:17 am

To begin with, you never want to test the gauge with a full twelve volts. It will fry the tiny wires in it. The juice it receives must first be reduced to 5 volts, via the vibrator.

Search "fuel gauge" or "fuel sender" problems to see how you hook up the gauge. Or take your apart to see the wiring.

Tim

Wed Jun 25, 2014 1:03 pm

Vibrator?

Wed Jun 25, 2014 1:25 pm

The "vibrator" is a device that used to vibrate when working to reduce volts. The new ones are encased in plastic (the OEM ones were metal) and they contain a light bulb that is similar to the long light bulb in your courtesy light. This light bulb uses up electricity, thus reducing the amount that goes to the gauge.

Many gauge or sender problems are the result of a failed vibrator that allowed too many volts and fried wires in, either, the gauge or even the rheostat in the sender. The new black-plastic encased vibrators merely fail and do not not allow any volts to damage your gauge, etc. The old OEM metal ones, when they failed, often allowed the full 12 volts through and cooked things.

The "ignition-on" wire for power goes to the vibrator--not the gauge. And another post on the vibrator goes to the power-side of the gauge to give it reduced power.

There are a number of posts on this forum that can show you diagrams of how this system is hooked up.

Tim

Wed Jun 25, 2014 1:57 pm

I found an old thread. Read both pages of it.

In the Search function on this forum, type in this:

fuel gauge vibrator ... 71 beetle

Sorry, I don't know how to transfer links.

The above thread will explain a lot, I think :?

Tim

Thu Jun 26, 2014 2:21 am

Hmm I see thanks, I'll have a look. None of my other gauges like tach, voltmeter etc have this vibrator, I just wired them up and they work fine. Is it just fuel gauges?

So have I probably fried my little wires or do the above mentioned test results mean it's still ok?

Thu Jun 26, 2014 7:42 pm

Yes, only the fuel gauge uses a vibrator.

And you may not have "fried" your fuel gauge. Unless you saw some smoke, chances are the gauge is still good. You can only tell by testing with the power going through a grounded vibrator, first.

Tim

Fri Jun 27, 2014 12:41 pm

Tim Donahoe wrote: Yes, only the fuel gauge uses a vibrator.

And you may not have "fried" your fuel gauge. Unless you saw some smoke, chances are the gauge is still good. You can only tell by testing with the power going through a grounded vibrator, first.

Tim
Hmmmm where do I get one of those vibrators!!

Fri Jun 27, 2014 1:02 pm

emu88 wrote: Tim Donahoe wrote: Yes, only the fuel gauge uses a vibrator.

And you may not have "fried" your fuel gauge. Unless you saw some smoke, chances are the gauge is still good. You can only tell by testing with the power going through a grounded vibrator, first.

Tim
Hmmmm where do I get one of those vibrators!!

Try a sex shop

Fri Jun 27, 2014 1:11 pm

Are you missing yours?

It's on the upper back of your speedometer housing. It's either a small, maybe two inch by one inch metal box, or the same size but made of black plastic. This device also has a thin metal (brass) grounding strap at its bottom.

If yours is missing, Wolfgang International, Wolfsbug West, Mid America--all of them sell the new black ones.

Tim

Fri Jun 27, 2014 1:14 pm

emu88 wrote: I got a second hand fuel gauge to supplement my stock one, and i did the following checks to see if it was working:

12v to plus terminal, G terminal to ground and needle moved up a little to zero.
12v to plus terminal, upside down T terminal to ground and needle shot up to full.

So gauge is good.

I then wire it up to the sender thus:

12v keyed to plus terminal
Black wire from sender to G terminal (other brown one goes to ground)
Wire to ground from upside down T terminal.

I turn the key on and the needle moves up a teeny bit to just before zero, despite the stock gauge showing a full tank, which is correct.

What can I be doing wrong?
Thanks in advance.

Tim's advice is good if you are using a stock VW gauge. If this is a standalone aftermarket fuel gauge however, it shouldn't need a vibrator to work.

First, if you are trying to run two gauges off of one sender, it may be causing problems. Disconnect the stock gauge and try again.

Second, the resistance range of the gauge and sender must match for it to read right. It may be that your second gauge, if it is aftermarket, is not the right range for your stock sender and may require a different sender to work. Does the gauge have any markings for its Ohm range?

Also, are you sure you have the sender wire hooked to the right terminal on the sender and not to a ground terminal?

Fri Jun 27, 2014 3:26 pm

Sounds like this is an aftermarket gauge.

What model number is it? VDO sells one (VDO 301-020) that is "supposed" to work with the stock VW 1968-newer sending unit, but when I bought one 3 years ago and tested it, I found it wasn't even close - I determined that it has the wrong faceplate on it the needle movement. I talked about that here:

http://www.thesamba.com/vw/forum/viewtopic.php?t=2...p;start=28

Fri Jul 04, 2014 2:58 am

glutamodo wrote: Sounds like this is an aftermarket gauge.

What model number is it? VDO sells one (VDO 301-020) that is "supposed" to work with the stock VW 1968-newer sending unit, but when I bought one 3 years ago and tested it, I found it wasn't even close - I determined that it has the wrong faceplate on it the needle movement. I talked about that here:

http://www.thesamba.com/vw/forum/viewtopic.php?t=2...p;start=28
It us a vdo, 301.292/4/2

It came out of a Lancia sports car, dated 1988, if that makes any difference?

Fri Jul 04, 2014 3:00 am

jhoefer wrote: emu88 wrote: I got a second hand fuel gauge to supplement my stock one, and i did the following checks to see if it was working:

12v to plus terminal, G terminal to ground and needle moved up a little to zero.
12v to plus terminal, upside down T terminal to ground and needle shot up to full.

So gauge is good.

I then wire it up to the sender thus:

12v keyed to plus terminal
Black wire from sender to G terminal (other brown one goes to ground)
Wire to ground from upside down T terminal.

I turn the key on and the needle moves up a teeny bit to just before zero, despite the stock gauge showing a full tank, which is correct.

What can I be doing wrong?
Thanks in advance.

Tim's advice is good if you are using a stock VW gauge. If this is a standalone aftermarket fuel gauge however, it shouldn't need a vibrator to work.

First, if you are trying to run two gauges off of one sender, it may be causing problems. Disconnect the stock gauge and try again.

Second, the resistance range of the gauge and sender must match for it to read right. It may be that your second gauge, if it is aftermarket, is not the right range for your stock sender and may require a different sender to work. Does the gauge have any markings for its Ohm range?

Also, are you sure you have the sender wire hooked to the right terminal on the sender and not to a ground terminal?
I am sure i have it hooked up to the correct terminal on the sender. No ohm markings on the gauge unfortunately :(

Thu Jul 10, 2014 8:46 am

Any ideas? I guess the gauge just won't work with the stock sender.

Thu Jul 10, 2014 11:07 am

Oh, sorry, I didn't notice you posted the part number of the gauge. Yes that is not correct for a stock VW tank sending unit. I don't think ANY other car was ever made that had a gauge that would work with an aircooled German Beetle sending unit. Only those 3020 and 301-020 gauges were for to go with the stock bug sending unit.

The 3020 actually says 301.252/39/9 12V 37/8 on it

The 301-020, the one I found to have the same "movement" of the needle in it as the 3020, but they changed the faceplate and it does not match, that one says:

301 220 002 60/90 - 0.5 OHM 12V

-Andy

Thu Jul 10, 2014 2:19 pm

Well, going back to your original description (sender wire grounded = empty, sender wire disconnected = pegged full), I'd say the gauge likely needs a 1966+ 0-90 ohm empty-full GM type sender or a 10-180 ohm 1987+ Ford type sender. These are the 2 most common with that directionalilty, it's no guarantee your gauge doesn't need something else.

Go down to radio shack and buy a 100 ohm (simulate 0-90), and 180 ohm (simulate 10-180) 1/4 watt resistor and connect each one, one at a time, between the G terminal and ground. Pick the lowest value that read full on the gauge and buy the matching sender. May require tank mods to mount the sender if the flange is different.

Second option (or if neither sender option above is correct) is to just buy a fuel gauge that matches the VW sender (75-10). Though I'm still confused as to why you need 2 fuel gauges in the car.

glutamodo wrote: I don't think ANY other car was ever made that had a gauge that would work with an aircooled German Beetle sending unit.

1986 and earlier Ford gauges use the same ohm range (75-10) sender as the beetle.

Thu Jul 10, 2014 3:56 pm

jhoefer wrote: glutamodo wrote: I don't think ANY other car was ever made that had a gauge that would work with an aircooled German Beetle sending unit.

1986 and earlier Ford gauges use the same ohm range (75-10) sender as the beetle.

Ah, I wish someone would have mentioned that in my other thread about the fuel gauges I've messed with over the years.

That does beg the question though, if the tank unit resistances were the same, why label an aftermarket gauge specifically as "special for VW"? I'd assume they would be OK for a Ford as well...

Thu Jul 10, 2014 6:15 pm

glutamodo wrote: jhoefer wrote: glutamodo wrote: I don't think ANY other car was ever made that had a gauge that would work with an aircooled German Beetle sending unit.

1986 and earlier Ford gauges use the same ohm range (75-10) sender as the beetle.

Ah, I wish someone would have mentioned that in my other thread about the fuel gauges I've messed with over the years.

That does beg the question though, if the tank unit resistances were the same, why label an aftermarket gauge specifically as "special for VW"? I'd assume they would be OK for a Ford as well...

Not all senders with the same ohm ranges work the same (linear vs non-linear), tank shapes can alter readings, and gauges may not be labeled or function linearly, so you can get inaccurate readings if you start mix and matching. IE, 1/2 tank of fuel may not show 1/2 tank on the gauge. Generally, if a gauge is labeled for say Ford, it's likely intended for the OEM Ford sender and tank and takes those differences into account so everything lines up.

Put a Ford gauge in a VW and while the Empty and Full would be ok you'd be kind of guessing in the middle for a while. Take a linear VDO gauge, with a linear universal sender and put it in a VW tank and you'll notice the gauge takes a long time to drop from F to 1/2 but drops very quickly to E once it gets below 1/2 due to the non-linear tank shape.

Fri Jul 11, 2014 8:30 am

Thanks both of you. Hmm in that case i'll shift my current gauge and save this project for another day! Annoyingly I bought a twin pod thing so one will have to remain empty unless I find a replacement another time.

Thanks again, this'll prove useful when I get round to doing it.