The gas sender is a variable resistor. This means that as the level of fuel varies in your tank the float at the end of your sender arm will move up and down which will vary the resistance of the sender which is what your gauge sees. The gas gauge will what to see a certain amount of resistance when the tank is full and another amount of resistance when empty. So, this is why the sender mush match the gauge for you to read the correct amount of fuel in tank. The vendor of your new gas gauge should provide you with the correct sender resistance if they are 'worth their salt'. From your pics I can tell you have a gauge gauge that requires a higher resistance full than empty. Be warned that OEM senders have been all other the place resistance wise. 0 to 90 ohm's is common today but I have seen 78 ohm's empty to 8 ohm's full (30's Packard's). There are many threads on this forum about gauge not reading correctly.
Ground is a term we use loosely to indicate where the negative battery wire goes on a negitve ground system. Some like it to go the frame, others (like myself) like it to go to a good size bolt on the engine/transmission as the starter is the most amp hungry device on your truck. I use one of the bolt from the bell housing to engine. NOTE: clean bright metal to metal connections are a must! No grease or paint accepted. Three items that should be electrically connected are the motor, frame, and cab. Most like those flat braided straps for this, again clean connections point. If the above is done correctly a ground somewhere close to the instrument cluster can be used under a convenient screw. Again watch out for painted areas.
EDIT...Ammeter: the ammeter is in series with the battery. It is NOT to be grounded. Charging current from the alternator goes to the negitive (-) side of the ammeter. The positive (+) side goes to your battery by way of your starter solenoid. The (+) side of the ammeter goes to the big copper lug on your starter selenoid. The battery's (+) side is connected by a #8 wire to this same large lug.The ammeter is there only to indicate what is going on with your battery charging circuit. No power leads to anything should be connected to the positive side of the ammeter. If a power connection is needed use the negitive side of the meter. Sorry, but I got my (+) and (-)'s mixed up.
Hopefully, this will get you started.
As a sidebar, car guys generally are great guys to get to know and hang out with. Hit some local car shows and cruise-ins. These guys love to fix cars especially if your buying the pizza and beer. You will be surprised and you can save the 85.00/hr for parts. Good luck.
Last edited by beltfed; 10/10/2015 6:47 PM.
