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Posted by Chris Case @ San Diego on Saturday, March 22, 2008 at 19:37:29 :
I had the wires reveersed. The SW they label one side with is not the sending 'switch', but the ign switch. And the side I couldn't read, labeled with something with an 'a' in it, is not bAttery, but 'ga' for 'gauge', which they call the sender. So SW to ign switch accessory, GA to sender.
I removed the lock ring from the tank, and soldered a male bayonet connector to it, for a ground that I ran to the frame. And lubed the ring with silicone dielectric compound. Good grounds are a joy to behold.
And I made a constant 5-volt source with Radio Shack components. A LM7805 'regulator chip', fuse holder,.1mfd capacitor and a little box to assemble it into, parts cost $7. A constant voltage source is supposed to be more accurate than a resistor, since the draw through the resistor will make different voltage depending on the resistance to ground via the sender. But I dunno what accuity we're talking about, +/- one gallon, or +/- 1/4 tank?
11 gallons in a 18 g tank reads about 5/8 tank. Right on at that. 25 ohms, measured through the system to the cab as ground. Time will tell if it reads good emptier. Some payday I'll see how it reads full.
Anyways, here's readings for those checking out their components:
Sender, 17ohms full to 80 ohms empty. That's the 'after' sender, a 'one wire' held on with the lock ring rather than 5 screws.
Dash gauge, one lug to case 80 ohms, other lug to case 104 ohms. Between lugs 24 ohms.
Paul has other gauges that read different, but ratios are about the same.
Those dash gauges have two coils in them, wound of about 700 turns of wire that is finer than my hair. And my childhood nick name was Whitey. And could be again.
Paul in NY has senders that read 0-240 ohms. I dunno. Mine works. So do his. Paul, are your senders two-wire?
I suspect it is possible that a one-wire sender could be made to work with a two-wire gauge if you leave one wire off, but you would need to check the readings of the coils and figure out the alternate wiring.
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