Gas tank float resistor help Carey ? Others ?

It sounds like the float arm is not adjusted for tank.  If the float arm angle was too tight, as the tank gets filled and the float gets up to half tank, the arm hits the stop at the end of the sender and can’t go any higher (in other words, the float gets submerged in the gas, but not at the top of the tank).  Once the gas gets down to 1/2 tank, the float is again free to follow the tank level down to empty.  The fix is to pull the sender and bend the float arm to match the tank and the swing of the sender.

You could alter the sender range using a resistor, but then the needle would go up to “full” on the gauge when the tank is half full and sit there until the tank is half empty and then start to move.  I don’t think that is what you want.

Gordon wrote:

You could alter the sender range using a resistor, but then the needle would go up to “full” on the gauge when the tank is half full and sit there until the tank is half empty and then start to move.  I don’t think that is what you want.

Yes this is the way I need to go, I need to know a resister value that will work with it as the 1st new float sender worked with the new set of digital GPS gauges but they that were crap with too many internal gauge faults that cannot be resolved ( I know wiring) So the eBay Seller did  refund the cost for them but with the hood in place the flat access is not visible but I can feel for the two male spade wire connections so that float has to remain, The 2nd new gauges I now have on order that I have used a dozen  times in the past have the different ohm rated fuel gauge hence my need to find a way the make the current tank float ( that can't be removed from the tank) compatible with the replacement gauge set. Someone with electronic knowledge hopefully can find the ohms conversion needed.

I never liked my 2004 IM fuel uage... full forevver but then.... went from 1/2 to empty in a jiffy, but then if those are my options they are better than 1/2 full forever ...

My fuel gauge in my Spyder is very consistent. When it gets down to 1/8 of a tank it’s empty. Ask me how I know.

I seem to have the talent of finding the bottom of most of my cars gas tanks, hoping to break that habit… I even found the empty on the Bmw r100rs and I had to stop to figure out what the reverse petcock setting was, I could not look at 60 mph

@Alan Merklin

I only have half of the equation.  I would need to know the actual resistance of the sender when it's reading "full" to be more accurate, so let's shotgun a solution for now by using a variable.

I would try a 50 ohm 1/2 watt potentiometer (pot) like one of these:

https://www.amazon.com/s?k=50+...amp;ref=nb_sb_noss_2

You don't need wire wound.  A simple version would work and cheaper the better as long as you can solder wires to it.  Run the center terminal to the hot side of the gas gauge and either of the outer terminals to ground to effectively halve the resistance of the sender throughout its' range.  Once installed and the gauge working, simply turn the pot stem one way or the other to dial in where you want the gauge needle to be.

If that doesn't do what you want, try running the pot in series with the hot lead coming from the sender to add 50% more resistance to the sender and dial it in the same way.  Remove the sender wire at the gauge and connect it to the center terminal of the pot.  Attach a wire to either of the side terminals on the pot and attach the other end of that wire to the gauge where the sender wire was to add 50 ohms to the sender.  Dial it in the same way.

That will shift the range back and forth on the gauge for you.

.

Gordon, I'm thinking there may be a simpler way.

Alan says the sender in the tank varies between 180 ohms at 'full' and zero ohms (shorted) at 'empty'. But his gauge will read 'full' when it sees 90 ohms and 'empty' at a dead short.

So.... if you put a 180 ohm resistor across the leads of the sender, the gauge will see about 90 ohms when the tank is full and indicate 'full'. (Two 180's in parallel make 90, no?)

As the fuel level drops, the total resistance the gauge sees will drop from 90 down to zero (a dead short across a 180 ohm resistor is still a dead short).

So, just placing that resistor across the leads should make the gauge show 'full' at full and 'empty' at empty, although it likely won't be linear in between. But what VW gas gauge is?

And he doesn't have to put that resistor across the sender leads at the tank. It could go across the leads at the gauge just as well.

Or, am I missing something?

Nope, you nailed it.  

I just went back and re-read the Bold script of sender and gauge resistances in the first post and you're absolutely right.  

About attaching it at the back of the gauge to avoid messing with the sender, too.  

I don't know why I didn't see that clearly, before - Duh!  

It sucks, getting old.....    Thanks, Mitch!

Gordon I don’t think Mitch was trying to give you any resistance. Good catch.  And yes, Volkswagen tanks used in our cars are never linear as we’ve talked about but as long as you don’t find empty, you’re good

Thanks !  It's bad when you lie in bed at 2:30 am trying to figure this out :~)              Sacto Mitch I sent you a pm ~

Tanks Inc., Meter Match, allows you to reprogram the Ohms value output to the gauge

I just looked at that module and it does a lot more than that, including smoothing the signal to the gauge to eliminate needle bounce and movement.  

Awesome product.

https://www.tanksinc.com/index...mode=prod/prd748.htm
Meter match fuel gauge

interesting … gas tank gauge fix for sure great stuff Carey

The master pulls through again. Well done, Carey!

Has anyone here tried the Meter Match module?  Did it work well?

Going to try the 180 ohm resistor as there is no access t the float to calibrate it w/o pulling a lot of the wiring, column and hood ...thanks !

@Teammccalla posted:

Has anyone here tried the Meter Match module?  Did it work well?

I think it's safe to assume that Carey has, since he linked it.

I believe that's what my Coupe had in it.

@Teammccalla posted:

Has anyone here tried the Meter Match module?  Did it work well?

Yes I've used it and it works for both a big discrepancy in sender/gauge Ohms ranges, or just to fine tune levels that can't be dialed in otherwise.  My only comment about it, other than "it works well" is that you need to set it with the car running as the fuel level changes slightly at 12v input vs. 14v input (when running)

@Alan Merklin posted:

Going to try the 180 ohm resistor as there is no access t the float to calibrate it w/o pulling a lot of the wiring, column and hood ...thanks !

The meter match can be wired at the gauge end and doesn't;t require access to the sending unit necessarily, as long as you can get to the sender wire between the sender and the gauge.

@chines1 posted:

The meter match can be wired at the gauge end and doesn't;t require access to the sending unit necessarily, as long as you can get to the sender wire between the sender and the gauge.

Thanks Carey !