Gas gauge help!

[DaGman]

I have been given a 1957 Fargo in boxes to assemble.  It came with a new stainless steel gas tank and no sending unit! Can somebody please tell me what the range of ohms is on the fuel sender on a 1957 truck is? Also I have tried several sending units hooked to stock gauge in the dash and it appears to me, to need a voltage reducer between the accessory circuit and the gauge. What voltage do the gauges operate on? Thanks for your help in advance!  I wish I had been there when this truck was taken apart....

[JBNeal]

Dodge trucks upgraded to 12V in '56, so your gauges shouldn't need an extra voltage reducer.  If the sending units you are using have a mismatched resistance range than the gauge, then the gauge will give you readings that won't make much sense.

 

additional information - fuel level sending unit resistance ranges

[DaGman]

I don't have a voltage reducer at all, at least not that I've found. When I hook a 73-10 sending unit up to test the gauge it slams to full instantly! I have tried the same sending unit with 5 volts to the gauge and it goes to full much slower . Moving the sender through its range of motion causes the gauge to either read full or empty but nothing in between.  The heat gauge does the same thing. The original heat sending unit reads 3750 ohms cold and the gauge barely moves when power is supplied. I'm missing something simple here I know it... but what?

[JBNeal]

fuel gauge reading full or empty with no readings in between kinda sounds like a ground issue...I had this issue with the '48 until I ran a ground wire from a stud I mounted on the sending unit flange to the battery, then the fuel gauge started working more accurately.

[DaGman]

I found my problem! The case of the gauge itself was not grounded! Lots of new paint! Lol. I didn't realize the case of the gauge needed to be grounded as well a the sending unit. The ohms required for the gauge is 10-73 and there is no voltage reducer used on the power side of the gauge as per another old truck I looked at . An old friend sent this to me from a 1951 Manual. Do not underestimate the value of old car guys and books!