Itinerant Air-Cooled

I have run across many people recently who are not happy with their new fuel gauge senders. A common complaint is that the new sender only displays half full when the tank is actually filled up. Another increasingly common scenario is that the gauge plummets rapidly towards reserve when there is still plenty of gas left in the tank.

SO . . . look at the gauge. It is not linear. From full to half takes only 1/3 the travel. Then, 1/2 to below reserve takes 2/3 the distance.

We know that a full tank should yield a sensor reading of 10 ohms.
An empty tank should yield a reading of 75 ohms.

The gauge needle is linear. A half tank *reading* on the gauge should occur by around 25 ohms, then we have a long trip to empty from there.

It is the SENDER that gives us a progressively faster descent as the fuel level drops.

Here is a factory sender. Ignore the burnt up mess, please. The small end is the full side. Each loop slowly adds resistance, and the heater slowly cools and allows the needle to move lazily towards 1/2. Then the loops get bigger and each loop causes a larger increase in resistance and the gauge moves more quickly towards empty.




You are viewing the "variable resistor" from the "front of the bus" back. The lever/float goes up to the right in this photograph, which is actually to the left when installed in the tank. The short end of the "variable resistor" is toward full.

Does anyone have a new sender sitting around? I was thinking, the above symptoms could occur if:
a) the new sender has a non-progressive "variable resistor"
b) the new sender has a progressive "variable resistor" installed backwards

I'd like to resolve this.
Colin

This would be great to solve. I am in that group of the tank half full needle while actually full. Does that make me an optimist?

Colin,

PM Gary (aeromech) on The Samba. He has two buddies who are electrical geniuses. One is Telford who participates on The Samba and another is a guy who works with Gary. Telford helped come up with a fix for the tube original senders in bay buses.

Really? This is a problem? Hmm, I installed a new sender in about 2009 and it reads Full when full and then when it hits Reserve I have about 3 gallons left.

Yes, this is a problem!

Every (new) sender I’ve seen has a square board with resistor wire wrapped around it- none of them have the original oblong quadrilateral shape like Naranja did.

BigEmma Crew and I half-heartedly bent the arm two years ago to get a more full reading, but it didn’t go far enough. They bent it more last week and I’m waiting to hear if they get an honest “full” reading.

Robbie

Jivermo wrote: ↑

Tue Jun 12, 2018 2:24 am

This would be great to solve. I am in that group of the tank half full needle while actually full. Does that make me an optimist?

You clearly are. If you were not, you would have exited the Volkswagen Bus freeway a long time ago.
Me? I'm full of it and yet, I'm half-empty.
Colin

asiab3 wrote: ↑

Tue Jun 12, 2018 7:45 am

Yes, this is a problem!

Every (new) sender I’ve seen has a square board with resistor wire wrapped around it- none of them have the original oblong quadrilateral shape like Naranja did.

BigEmma Crew and I half-heartedly bent the arm two years ago to get a more full reading, but it didn’t go far enough. They bent it more last week and I’m waiting to hear if they get an honest “full” reading.

Robbie

Hah! A hA!. HA!! Really?
Colin

The grammar and geometry closet of my brain is cringing right now. The senders have “squared off corners.” The boards themselves are rectangular and not perfect squares.

But yes.
Robbie

Bleyseng wrote: ↑

Tue Jun 12, 2018 7:01 am

Really? This is a problem? Hmm, I installed a new sender in about 2009 and it reads Full when full and then when it hits Reserve I have about 3 gallons left.

Oh Geoff.
This is no time to preen about the good old days of 2009.
It's all gone to hell since then . . .
Colin

asiab3 wrote: ↑

Tue Jun 12, 2018 2:40 pm

The grammar and geometry closet of my brain is cringing right now. The senders have “squared off corners.” The boards themselves are rectangular and not perfect squares.

But yes.
Robbie

Nobody here is getting on your case about the word choice.
My ha ha haha hahaaaaaaaaaa is merely an unpleasant gloating at a possible verification of my suppositions.
Colin Hahaaaaha