Hello All, After spending some time trying to repair my sending unit, I decided that re- wrapping it was a horrible idea! So it was off to the yard in search of a working '78 sending unit, After finding only one truck with no fuel tank I looked around and found no replacement anywhere as a single unit.... At this point it was back to square one I decided to rethink things and looked at a 79-85 sending unit and noticed it was the exact same rheostat on a separate hatch, It was off to the yard once again this time I stuck gold and found a rheostat from a newer truck. Here is how you go about replacing a damaged rheostat to get that fuel reading back! Here is what you will need! Just the basic stuff Bend this tab flat and pull the cover back You might need to pull these tabs out with your thumb All Is clear now!! Or maybe not so much??? After opening the unit up you might see the problem right away, It might not be something as simple as Broken/Dirty Rheostat wire/solder connection ect... Moving the paddle out of the way can help abunch! Note the damaged paddle it's almost gone from wear... There can be other issues hiding make sure to inspect the paddle for excess wear/contact and check the resistance across the Rheostat should read 1~Ohm at full tank an 100~Ohms at empty each wire a progressive jump. From here if either the coil or paddle is Damaged/Worn removal and replacement is required, First bend the two metal tabs..... (If the coil is fine carefully remove solder an set aside the coil--replacement paddle/float body required!) Prepare the new unit for installation(Rheostat coil/Float body) At this point install the coil in the unit re-bend the tabs back and solder the new unit together, Make sure it is secure and the solder makes good contact! Now check the free play of the float arm and the paddle drag across the coil Make sure it is just enough pressure to make contact and not grab the wires.. IT HAS TO BE JUST RIGHT OR IT WILL NOT WORK/RIP APART!!!! After all is said and done replace the cover and rebend the tab that holds it in place, Install the unit to your year pump housing or unit hatch and make sure everything is clean and that all connections are solid.... Test and it works like new yes sir! Hope this wasn't a total waist an helps someone out who has maybe ran into this issue or has a sending unit that reads with a mind of its own ex 1/3 full or empty always. Have any questions feel free.... NOTE...The blank rheostat block in the photos is not a functioning unit. I used my old broken unit for this write up as I forgot to take photos during my repair make sure your rheostat is wrapped and functioning I will add photos after I repair another unit.
Very helpful. I had to swap my 78 fuel pump again in a few days, my gas gauge works but I will inspect this setup to see how its looking. Very good info.