Fuel gauge backwards

[Hanker]

I know I must be missing something simple......

But, I am replacing the fuel sender and decided to test first. The old sender had two wires on a common post (green & Black), ground I'm assuming. Then there is a red wire that goes to the center post, I'm assuming hot.

So, in order to test I just put a jumper on the red and hooked it to the new sender. I did the same with the black and green wire. Walla, it works.......... oops, it's backwards.

When the ball is down (bottom of the tank, empty) the gauge reads FULL. When the ball is up, the gauge reads EMPTY. It moves as I move the plunger, but opposite the direction it should go.

Any ideas.......

[ToonaFish]

Hanker:
I know I must be missing something simple......You bought a boat from Poodle and you wonder why it's bass ackwards? Hmmh, I have some swampland in Iowa you might be interested in...

Bunches,

Celene 'Poodle wanted to get better gas mileage, so he turned it upsidedown, silly'

[BUIZILLA]

Rob, just be thankful it's not old world Lucas electric's.. it would be on fire by now :D

methinks your ground test is bassackwards..

J

[Greg K]

Is the new sender mounted to the tank or are you doing this with it off and out of the tank?
If not, either run a wire from the mounting flange on the tank and to the flange on the sending unit, then test it. Or, mount the sending unit and then test. Sending unit needs a proper ground.
Is the sender the same type you're replacing?

[Hanker]

Originally posted by Celene
'Poodle wanted to get better gas mileage, so he turned it upsidedown, silly' You may be on to something. After filling this thing a couple of times, I realize a correctly working fuel gauge is imperative! I've got to learn secondaries are only for occasional use............

Greg,
Fuel gauge is a Gaffrig, and the sender I am using is a VDO. The sender is not mounted in the tank yet. I am including a graphic (http://www.donzi.net/photos/fuelgauge.jpg) of how I have hooked it up - it looks the same as the Gaffrig site.

I'm beginning to belive the gauge is reverse wired internally. I hate when I can't complete a project!

Still open to suggestions.....

[Islander]

You could just turn the tank upside down. :)

[MOP]

Hanker by now you leg is getting kind of long! The gauge completes ground to the gauge. I would think the gauge wire should go to the center terminal and the other to asure the sender is grounded properly. No positive power is sent to sender.

You guys Quit picking on the Poodle, I was going to invite him back for some more of our lovely weekend weather! :D :D

[Greg K]

Just a bit more info, I think the tube sender you have is adjustable and works on 90-0 ohms.
The Gaffrig gauge is operating range is 240-33 ohms.
It's possible the two are not compatible.

[Hanker]

M.O.P.

I would agree with you. Here is a PDF (http://www.donzi.net/photos/gifl.pdf) from Gaffrig. It looks like the way I have it wired? I can't see any reason it would need to be installed in tank to work. In fact, it works great if I could live with the gauge reading FULL when I'm empty.

Greg,
Maybe it's not compatible with Gaffrig. But, why would it go backwards. BTW, I connected the old sender to the gauge (don't know manufactor) and it appears to do the same thing. At the same time, if I short the two leads together it pegs to Full. :confused:

[ToonaFish]

If you were South Of the Equator, would it read correctly?

Bunches,

Celene 'ambient forehead temperature is 100.7'

[Donzified]

No positive wire to gas tank sending unit.

That reminds me of todays report of a guy siphoning gas out of a gas hauling truck in Bagdad...blew himself and the truck up because he was smoking a cigarette.

I love gasoline! but don't we all.

[mattyboy]

well according to my wife

E = enough

Matty

[Ranman]

Just ride around with a 1/2 tank and it will be accurate.

[Hanker]

Update,

Called Gaffrig, and they told me that ANY sender will work with their gauge - except VDO! VDO's sender sends a signal reverse from everybody else. Bought a Telflex - I don't really care for it, but I guess it will work.

Also, I feel the need to clear something up. There IS Voltage and Current to the sender. These are electronic gauges, therefore, in order to "read to ground", you must apply a voltage to measure the current through the resitance in the sender. You cannot read anything with out appling "hot" (voltage) somehow.

Don't know why that was important to point out.....Aaauugghhh, the EGO's got me!

I guess it's all the money my dad spent on my edgamacation.

[MOP]

What the sender does is increase or decrease the amount of ground supplied to the gauge through the rheostat in the sender. I have never seen or heard of + positive voltage being supplied to the sender. Positive current is supplied to the gauge. With the key on it is possible to actually get a spark off the ground wire at the tank because the voltage which is supplied to the gauge can complete its circuit. In safety classes it is recommended to test the fuel sender circuit using a jumper from engine ground not the to test within close proximity of the sender opening. Tank ground should be checked both at the tank and at the filler with an OHM meter the reading should be the same as touching the probes together in other words total and complete. Many gauge problems are due to faulty grounding of the tank.

[Ranman]

SOme senders DO require 12V to the sender. Here's an excerpt from Gaffrig. http://www.gaffrig.com/cat_senders.php


The biggest advantage to this new line of senders is the absence of moving parts. As it has no moving parts, the unit is impervious to mechanical failure and it greatly reduces needle bounce on the gauge. The probe comes in 12 inch increments and can be cut into any length down to the net lower increment. The probe can be built to fit tanks from 4" to 120" deep and is available for standard as well as custom tank installations, requires 12 volts to sender. Did someone mention that there is such thing as the "no moving parts" tube sender that does NOT require 12V?