So I have what seems the typical non-working fuel gauge in my 55 F250. The needle raises to full at startup but eventually falls to empty. Sometimes it may register half or less for awhile. Anyway, I purchased a new sending unit from LMC as the first troubleshooting step. Now through searching (and the new unit didn't fix the problem) I find that aftermarket sending units will never work? Does this include the LMC and other model specific vendor models? My truck is already converted to 12v, did this play a factor? I still have the original unit, should I start checking frayed wiring too?
Is my easiest option a replacement "universal" gas gauge for now? I really need a gauge for a frequent driver truck.

 

In my opinion, pay the extra and purchase the gauge and sender combo that Mid-50 sells. I spent weeks trying to figure the correct ohms, the correct sender, etc. Are you running 12 volts to your gauge? Most gauges require you to actually drop the 12 volts down to 6 volts. The Mid-50 combo takes the guess work out. Good luck and check your grounds.

 

You need 6v going to your gauges not 12v. See Ross's excellent post (#2) at https://www.ford-trucks.com/forums/1075111-6-to-12-volt-conversion.html

Also here is a link to a pdf document on converting 1955s:
https://www.ford-trucks.com/forums/attachment.php?attachmentid=37624&d=1307471855

 

I think ll be in touch with mid-50's on their gauges and senders combo. On my cluster currently the only thing working is the speedo. The previous owner mounted a temp and oil pressure gauge but I like the idea of the stock gauges. If I need to replace the fuel I may as well work on the whole setup. I'll talk with them, but does anyone know if those units work for 12v systems already?

 

I'm not sure which gauges you are considering at Mid-50s but if they are stock replacements they will require 6v converters.

You might want to shop around a bit. Dolphin gauges are less expensive but equal quality (http://www.dolphingauges.com/index.html and they are 12v, need no converter and come with sending units if you order them that way. There are many others. It all depends upon the style that you want.