Hi all;
I bought a set of 6 Dolphin gauges for my 50f1. I installed them and the gas gauge goes all the way past full, but I haven't put any gas in the tank yet is this normal or is there something wrong. Thanks RUSTY

 

 

I think what Old F1 is trying to tell you is that the gauge and the sending unit have to be a matched set.

Are your gauges set up for 12 volt and the sending unit 6 volts - not going to work.

Is the resistance range (ohms) in the sending unit not the same range as the gauge - not going to work.

If you bought the sending unit that goes with the gauge from the manufacturer, and it is going to full when the tank is empty - flip flow the power and sending unit wires on the back of the gauge.

And you realize of course that power flows from the switched power source to the gauge, then out of the gauge to the sending unit which is grounded (through the tank).

Just thinking out loud!

 

there is no power on the wire to the sending unit. The fuel gauge is calibrated to compare the actual ground vs the partial (resistance to) ground supplied by the sending unit.

You'll notice that these are really small amounts of resistance being measured.. 30 or 240ohms max.

(and the autometer, typical aftermarket, does it reverse of the manufacturer supplied parts, going from high to low resistance (240->33), instead of low to high, 10->70, or 0->30)..
Dolphin gauges use this 240->33 calibration.. thus it is sending a HIGH value when empty that the gauge is designed to register as FULL.

Sam

 

So Sam is it right or is it wrong.

 

which 'it'?

the sending unit is right
and the gauge is reading the values right
but they are speaking different languages..

SO, you have to change one or the other..
dolphin only makes gauges supporting 240->33.

Sam

 

Uhhhh I don't know if I'm going to agree with you on this one Sam unless this gauge has a special set up where it is gounded at the panel as well. On a stock set up (and I know this is not stock) There is power in the wire that flows to the sending unit. If you check it with a meter, it's registring a full 12 volts (or 6 as the case may be) where the wire attaches to the sending unit. The variable resistance of the sender is what allows different flows to ground and thus the indications on the gauge. Unless the gauge has a seperate ground, the only way to complete the electrical flow circuit is through the sending unit. The sending unit is not hooked to a power source, it does have power though that flows from the gauge and sends it to ground.

But as far as his problem is concerned, I agree the sender and gauge are not compatible. Rusty, you have to buy the sending unit that is made for this gauge.

 

darn, I just put my bed on so can't get to the sender ..

I've never heard of power at the sender. but i've been wrong before..

sam

 

I think we are talking the same thing Sam but saying it differently. I'm talking "electrical signal flow" and I think you are thinking I'm talking about power being applied to the sender then flowing up to the gauge...no no no no no.....

The power flows from the distribution point (in this case either the ignition switch or a fuse bar) up to the gas gauge (left lug) it flows out the gauge (right lug) and then flows down to the sending unit. In the sending unit itself, a full 12 volts (6V) flows into a wire that is wrapped around a moon shaped metal face plate. The float arm contacts this moon shape winding with a sliding point that changes position as the float raises and lowers. The lower the float, the lower on the windings the contact is made and the more wire (thus more resistance) the power has to flow through to get through the coiled wire and out through the sending unit housing - to ground. That is the flow path of the power from source to ground in the gas gauge circuit. The power isn't hooked up at the sender, it comes down from the gauge - flows through the sender - to ground.

So, if you take your wire off the top of the sender and touch it to ground (don't do it for more than a second) you will see the gauge rise to full in about 1 to 2 seconds. With a meter, if you measure the voltage at the stud on the top of the sending unit,to ground, you'll see a full 12 to 15 volts - depending on battery health.

 

Sorry Julie; I don't have any power to the sending unit wire. The gauge goes to full when the key is turned on. Even with the sending unit wire OFF the unit.(not on it at all). I'm going to take the sending wire off the back of the gauge and bypass the ez wire fuse box with a single wire back to the sending unit and see if it makes any difference. RUSTY

 

i have a 51 with the same guages and the same problem..
i have the dolphin 5" dual mechanical set....
everything works fine except the gas guage...turn the key on,,goes to full..
sending unit and guage are supposed to be matched....????
could it possibly be incorrectly grounded.??tks,ashlandcat

 

where did you get the sending unit? the one with the Dolphin kit, or the original in the tank?

I put a mustang tank in my truck, and couldn't find a set of gauges that I liked that would work with the stock sender (10->70 ohm ford).. so I cut a hole for the standard aftermarket sender (240->33 ohm). then the gauges I got work as expected..

Sam

 

Rusty, looks like you may have to take the sender out ,connect an Ohm meter to the connections and find out what'cha got?? at full and empty??

 

Unless those tricky Chinese Communists have invented a gauge that can read minds, the gauge has to be electrically connected to the sending unit some how, and power HAS TO FLOW through the sending unit for the gauge to work. If it doesn't, you have it hooked up wrong.

We still don't know if you are using an new or a stock sender. THE STOCK 6V SENDER WILL NOT WILL NOT WILL NOT WORK with that 12 Volt gauge on a 12 Volt upgrade. It is designed for compatable resistances, and compatable resistaqnces at 6 volts ONLY.

Again, YOU HAVE TO HAVE THE SENDING UNIT THAT WAS DESIGNED FOR THAT GAUGE. IF the manufacturer told you the gauge fits a 1950 Ford truck, they are talking about physical configuration, not electrical compatibility. It has to say "Works with the stock sending unit."

If you want to test it to see if it is the right sending unit, try this:

Take the gauge and the sending unit out of the truck. Get a little 9 volt radio battery and three jumper wires with alligator clips on the ends. Connect the negative side of the battery to the mounting plate of the sending unit. Connect the negative lug of the gauge to the wire connector on the sending unit. Connect the third wire to the positive side of the gauge and position the arm of the sender in the "FULL" (up) position.

Now touch the positive side of the battery with the loose alligator clip (the other end of which should be connected to the positive lug on the gauge). See if the needle moves - it should but slowly. If it stays close to empty, reverse the connections on the back of the gauge and try it again - it should move toward full (but only go to 3/4) if you have the right sending unit.

AGAIN, you have to have the sending unit that was made SPECIFICALLY FOR THAT GAUGE -both 12 volt - or both 6 volt - same resistance range.

Power flows from the distribution point - to the gauge side "A" out of the gauge side "B" -to the sender - to ground - period.

 

I'm sorry Julie;; It is the sending unit that came with the gauge kit. It all came in one box. RUSTY