[cornfieldcars]

I removed the original gas tank from my 48 P/U and it appears to be in pretty good shape inside and out with the exception of the wire going to the sending unit. I cleaned the tank up, painted it and am coating the inside with sealant. My question is about the sending unit. It doesn't look bad mechanically but not sure how to hook it up as it's 6 v. Are there more modern sending units that would bolt up to this tank that I can use or how do I go about converting to 12v? Thanks in advance.

barry

[zonk]

Don't know if this will help if your talking chevy pickup?
http://www.oldchevytrucks.biz/catalog1/0109.html
http://www5.mailordercentral.com/rbs...item=2&mitem=8
http://www.chevyduty.com/

[cornfieldcars]

Thanks Zonk,

I coated the inside of the tank last night with sealer and made the decision to buy new guages, when I get that far, and use the sending unit that comes with them. Later.

Barry

[docvette]

Doc here,

Voltage is NOT an issue on the sender..Resistance is...

The sender is nothing more than a variable resistor (the arm / float assy) mounted on a center wiper (the fuel pickup or sender mount) works like a volume control on a radio..

The signal processed through the sender to the gauge is ground and a variance to ground from the arm..to the Whetstone bridge internal the fuel gage..

a whetstone bridge is a perfectly balanced network of 4 resistors, (shaped like a triangle on paper anyways..) The Network is coupled to the gauge (a wound coil and PM ) which straps across the total network, and power, the missing equation is ground...provided by the sender..The more ground (low fuel) the more unbalanced the bridge..the resistance of the gauge trys to compensate for the balance by more current to the meter coil (hence ..meter movement..) Same applies the other way..

When you get your sender, be sure it is Comparable to the Gauge resistance you are using..(new or old)

The more important and most overlooked item is a GOOD tank to frame ground..Remember it sits on rubber straps, The filler floats on a rubber grommet, and if a rubber hose is used anywhere in the line (like at a fuel filter) the tank has no ground.

To test an old sender, use a DMM set for R x1 on the ohms scale, clip a lead to the sender terminal and the other to metal ground..raise and lower the float assy, Depending on your sender it should read between 0 to 30..0 to 60...0 to 90..up to 270 ohms..It should operate smoothly , (no meter jumps or dropouts) as you raise and lower the arm..

The only other test is the float itself..is it filled with gas? does it float in a bucket of water? If no, get a new float or sender.

Doc

[ChevelleSS_LS6]

Originally Posted by cornfieldcars

I removed the original gas tank from my 48 P/U and it appears to be in pretty good shape inside and out with the exception of the wire going to the sending unit. I cleaned the tank up, painted it and am coating the inside with sealant. My question is about the sending unit. It doesn't look bad mechanically but not sure how to hook it up as it's 6 v. Are there more modern sending units that would bolt up to this tank that I can use or how do I go about converting to 12v? Thanks in advance.

barry

update your project journal

[cornfieldcars]

Doc,

Great explanation on bridge! I doubt if too many people have heard of it before. I guess the reason I mentioned all this was because in "old" gauges didn't they just use bimetal strips to move the needle? If so, given the same resistance (the sending unit), and moving to 12v from 6v would make more current flow and produce inaccurate readings. Thanks

Barry

[docvette]

Doc here,

Barry,

You are absolutely Correct!!..

Given todays Vehicles..Totally inaccuracy's would exist..big time!

I almost completely forgot about the bi metallics , since it's been years Since I worked on a set..

Last one was on a 50 Ford Sport Coupe I had ..on a 390 transplant where an inline once lived..The goal was to keep it looking stock...

They are also prone to Other inaccuracy' s they don't exactly tell ya about..Like the Illumination lamp heating up the Cluster pot and mount and adding a bit..or direct sunlight "Creep"..

The addition of Computers sure have changed the way we think ... Even in cars now...we tend to forget the "Basics"..

Doc