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Sat May 09, 2009 3:39 pm

Hi there,

I've been driving my bus for 5 years without a fuel gauge and have decided enough is enough, but have some trouble identifying the correct way to wire an aftermarket gauge up. My van is a '65 without a fuel gauge in the speedo and has been converted to 12 volts.

I've just spent today taking the engine and fuel tank out to replace the old faulty sender with a new 12 volt VDO Siemens unit. There is an earth lead connected to one of the bolts of the sender unit that goes to the metal of the engine bay, and a brown wire connected to the sender that goes to the front of the bus. This brown wire is connected to the ground terminal on the aftermarket sender and the other terminal on the gauge is connected to the fuse box.

When the ignition is turned on the gauge jumps to full regardless of how empty or full the tank is.

My question is what have I done wrong? Is the gauge wrong or does it need adjusting? Have I wired it up the wrong way? I can't find a wiring diagram for a gauge in any transporter manual, and have used one out of a 411/412 manual as a reference which seems to be wired the same, apart from it being a gauge in the clock as opposed to an aftermarket one.

Any help would be great as I'm about to take a ferry France on a road trip and would love some idea of how much fuel I've got in the tank. (It's a luxury most people take for granted!) Thanks!

Sat May 09, 2009 3:51 pm

If the needle jumps to full when the key is turned on then your sending unit wire is probably touching ground somewhere. Maybe the wire chafed through on a sharp metal edge. Usually on the back of the gauge, there will be a push on tab or post marked "s" for the sending wire. If you disconnect that wire with the key on, the needle should fall to empty. Try running a temporary wire outside of the bus and straight to the sending unit and see if it works. At least then you can isolate the problem. I don't have a VDO gauge but most gauges usually have three wires, + or positive for key switched on power, - or negative, and the sending terminal. Some older metal gauges are grounded through the case and might have just two terminals.

Sat May 09, 2009 4:01 pm

Thanks for the quick reply!! I'll try that out tomorrow and see if the sending wire needs replacing. It's been in the van for over forty years and has been painted several different colours, like my van. The VDO has just two terminals, A positive and a ground.

Sat May 09, 2009 7:24 pm

Did you remove the shipping pin?

Sun May 10, 2009 2:02 am

Yep! I pulled out the pin and heard the float drop to the bottom.

Sun May 10, 2009 7:28 am

scott_fury wrote: My van is a '65 without a fuel gauge in the speedo...There is an earth lead connected to one of the bolts of the sender unit that goes to the metal of the engine bay, and a brown wire connected to the sender that goes to the front of the bus. This brown wire is connected to the ground terminal on the aftermarket sender and the other terminal on the gauge is connected to the fuse box.

If your bus is a '65 it should have a gauge to the left of the speedo.

The earth lead should be replace as you describe it.

The sender wire should be connected to the sender's terminal not ground.

The other end of the sender wire should be on the gauge's "sender" terminal.

The switched power should be on the "+" terminal and the ground wire or mounting fixture should be grounded.

Earth and ground are the same. The sender terminal is not ground.

Sun May 10, 2009 7:36 am

K6 is the fuel guage. It grounds to the dash through the bracket. Stock there is no ground wire, though sometimes people install them. Sometime syou need toe scratch the bracket aginast the under side of the dash to get a good ground.
If it doesn't have a good ground it'll ground through the sender wire or light wire and read funny.

Wire to sender should be plugged into the sender connection.

Sounds like the sender is connected properly.

Sun May 10, 2009 8:16 am

Good time to also install a reserve switch. Even if you do not install the cable also you can just flip it by hand up by the starter.

That way you can have that gallon left over if you run too low on fuel, and shut of the valve when removing the engine for an almost drip free gas line disconnect.

Sun May 10, 2009 10:50 am

Success!!! Thanks for all the help. To be honest I was being a bit of an idiot! I think the earth/ground on the gauge was not good so gave that a good clean with a wire brush and fixed new connectors to the sender wire and +positive wire and hey presto, the gauge reads just over a quarter full, which, by my estimates is spot on.

Thank you for the advice and wiring diagram, etc. I could've been trying to solve this for a long time. No matter how hard I stared at it, I couldn't work it out. It's helpful suggestions from all you guys that have saved me from another sleepless night dreaming of fuel gauges and sender units!! More importantly I now know when I need to fill my bus up, instead of coming to a spluttering stop and having to pour a jerry can in to get to the nearest gas station.

Cheers!!

Tue May 26, 2009 6:54 pm

I've been researching a problem and came across this post - lots of good info!

I have a problem with my fuel guage in my 63 Single Cab. When I turn the ignition on it appears to go more "empty." In other words, with the key off, it reads empty (always has), and when I turn the ignition on, it ever so slightly moves farther left to empty.

When the key is off I can tap the gauge face with my fingers and the indicator will bounce. When the key is on, it won't budge.

Prior to this Spring the truck had been sitting for a few years. Here's what I've done related to this:
- I removed the tank and sender for restoration. Sender is clean and functioning. Wiring returned to stock with good ground.
- I ran a new wire direct from the sender to the gauge with no change/improvement.
- I've run a new wire from the "+" to a hot "+" on the fuse panel, and no change/improvement.

The gauge functioned perfectly before I parked the truck a few years ago.

Its a 6V gauge and my truck is 12V. There is a voltage drop under the dash from the prior owner. Its very difficult to see the wiring under the dash and I can't tell what's all running through the voltage drop.

While I don't believe its related, when I installed my new engine I swaped out a 12V generator set up to a Bosch alternator with an external regulator. I've wired that up correctly and its charging perfectly.

Is this a ground problem? (the sender ground wire is attached the the body - center section)
Do you think the gauge is bad?

In the comments above the gauge was pegging at full. Mine is pegging at empty.

Help please!!!!
:?

Tue May 26, 2009 7:40 pm

Reversed polarity?

Tue May 26, 2009 7:51 pm

LittleThunder wrote: Reversed polarity?

Huh? How does this happen? What's the fix?

Wed May 27, 2009 6:39 am

Here's a simplified schematic. I hope it helps.
https://www.thesamba.com/vw/gallery/pix/260870.jpg

Thu May 28, 2009 5:50 pm

Quick update...

Tonight I was messing around trying to diagnose what's going on and when I turned on the headlights my fuel gauge when to "full". WTF? That's something I didn't notice before. And when I disconnected the gauge light wire it went back to normal.

I think I just need to remove the parcel tray, remove the kick panel and just dig into the wiring. Something's a miss... I simply can't get a clear view of the wiring with the parcel tray in place.

:x

Thu May 28, 2009 6:51 pm

Quote: Quick update...

Tonight I was messing around trying to diagnose what's going on and when I turned on the headlights my fuel gauge when to "full". WTF? That's something I didn't notice before. And when I disconnected the gauge light wire it went back to normal.

I think I just need to remove the parcel tray, remove the kick panel and just dig into the wiring. Something's a miss... I simply can't get a clear view of the wiring with the parcel tray in place.

I bet you have a poor ground at the gauge or sender. Try holding a length of wire, bare on both ends, to the gauge case and other to a good chassis ground. The same with the sender. Any difference?

Thu May 28, 2009 6:53 pm

wardvwracer wrote: Quick update...

Tonight I was messing around trying to diagnose what's going on and when I turned on the headlights my fuel gauge when to "full". WTF? That's something I didn't notice before. And when I disconnected the gauge light wire it went back to normal.

Sounds like the gauge is not grounding to the dash. Sand off some of the paint where the gauge bracket presses against the dash. A dab of grease on that bare metal is good way to keep corrosion away.

Thu May 28, 2009 7:07 pm

Thanks guys, I'll give it a try.

Tue Jun 07, 2011 7:02 pm

Did you fix it??

Sat Jun 18, 2011 3:09 pm

I am having a bit of the same problem with my 1966 double cab. My gauge jumps to full with a empty tank (1-2 gallons of gas) when the key is in the "on" position. I have a equus fuel gauge and vdo tubular sending unit.

The gauge was working prior to me pulling the tank, cleaning it, and sealing it.

I ran a length of wire from the back of the gauge sender contact to the sender unit. Still same result. I pulled the sender wire and ground wire from the gauge and still jumps to full. I have also tried grounding the wire to a different spot but same thing.

Any ideas??

Sun Jun 19, 2011 6:30 am

HiPakeDC wrote: ... I pulled the... ground wire from the gauge...

The gauge is grounded by the bracket. Loosen the bracket and scratch it into the metal better where it touches the back of the dash.