Another Fuel Gauge Problem????? HELP!!!!

[70396CST10]

Well, This is driving me crazy..

I have been trying to get my fuel gauge working with no luck.. The guy I bought the truck from said it just needed the float replace..

So I buy a new float and install it.. Nope, does not fix the problem and yes, the float did float...

So I pull the wire off the sender and it goes to the 3 o'clock position so that is good..

Then I ground the wire and it goes to empty and that is good..

Next I check the fuse and that is good..

Then I check the ground wire on the fuel gauge itself and that is good..

Then I try grounding the sending unit and that makes no change.. And yes, I checked the float after installing it by removing it and putting it in water.. No luck..

So then I order a new sending unit and that does fix the problem..

So then I take a fuel gauge I have from my 69 camaro and take the resistor off it and change the resistor and that did nothing..

Gauge is stuck right at about the 1/8 mark..

I have about 6 gallons of gas in the tank..

I tried manually moving the sending out of the tank with it grounded and hooked to the brown wire and it will go just past 1/4 tank with the arm all the way up??

How should the wiring be on the back of the fuel gauge.. I have 3 posts.. Bottom post is grounded to the cab.. Top 2 posts have the resistor and circuit board attached to them..

I am at a loss.. I have tried everything the board research has showed me with no luck.. So far I have a new float, new sending unit and no worky gauge..

Very frustrated and aggravated with this gauge not working after all the wasted time put into it..

Can someone explain how the back of the gauge works?

I assume 12 volts into one side and the resistance is on the other side with a ground on bottom???

Thanks for any help..

James..