I'm not sure as I follow you on this. It looks to me that the two coils are
nothing more than induction coils, that generate a magnetic field which varies
with the amount of current coming from the fuel tank sender. The needle itself
don't think is actually part of the circuit, but is passively acted upon by the
magnetic field generated by the two coils. There is probably some kind of
resistor in front of the two coils used to burn off some current, so that the
hair-fine wire on the two coils doesn't fry. I didn't look at the back of the
needle assembly, but I bet there is some kind of resistor mounted there.
Actually now that I've talked about this it does give me a better idea if how
this should work. I'm going to take another look at my gauge again tonight.
Thanks for the input.
>To: "Bryan Vandiver" <Bryan.Vandiver@eng.sun.com>
>Cc: "spridgets list" <email@example.com>
>Subject: Re: fuel gauge questions
>X-MimeOLE: Produced By Microsoft MimeOLE V4.72.3110.3
>It occurred to me that the insulated coil may actually be the resistor, and
>the other coil may be the heating coil. If so, the metal piece that
>attaches to the needle would be going through (or lie near) the bare coil
>instead. If this is the case, then the connections would be: Battery to
>"B" terminal, then "B" terminal to insulated coil, then insulated coil to
>other coil, then other coil to "T" terminal. The main point is that the "B"
>terminal has to connect to the resistor before connecting to the heating
>coil or the heating coil will get too hot and "fry" itself.
>From: Wiedemeyer <firstname.lastname@example.org>
>To: Bryan Vandiver <Bryan.Vandiver@Eng.Sun.COM>
>Cc: spridgets list <email@example.com>
>Date: Tuesday, August 10, 1999 11:12 PM
>Subject: Re: fuel gauge questions
>>First, nothing should be grounded to the fuel gauge case. Second, your
>>gauge is a thermostatic type, which means that as the current passes
>>the insulated coil, the coil heats up, which causes a bimetal strip that
>>should be either running through the center of the coil or somewhere near
>>the coil (but not necessarily touching the coil) to heat up also. This
>>bimetal strip is attached to the needle. As one side of this bimetal piece
>>heats up faster than the other side, it bends, which causes the needle to
>>move, indicating the amount of fuel. The path of the current should be
>>the battery to the "B" terminal, then to the first (left) coil, (which is
>>simply a resistor to reduce the voltage) then to the heating (right)coil,
>>and finally to the "T" terminal. So, one end of the wire on the left coil
>>should be attached to the "B" terminal, and the other end should be
>>to the right coil. The other end of the insulated right coil should be
>>attached to the "T" terminal. The needle itself should not be attached to
>>any wires. Hope this helps.
>>From: Bryan Vandiver <Bryan.Vandiver@Eng.Sun.COM>
>>To: firstname.lastname@example.org <email@example.com>
>>Date: Tuesday, August 10, 1999 2:40 PM
>>Subject: Re: fuel gauge questions
>>>The back of my gauge is marked B and T.
>>>As far as the series connection goes..
>>>Is the left coil 'grounded to the case through it's screw mounting??, or
>>>each coil have a wire soldered to each side of the needle assembly?
>>>Looking at the inside of the gauge from the front, it appears the left
>>>only one (1) wire coming off it (should there be two?)
>>>If there is only one wire, I assume this should be soldered to the point
>>>of the right coil, and the 'wire comming off the insulated tab on the
>>>is soldered to the point on the rt side of the needle assembly??
>>>I'll try doing a primative diagram:
>>> | needle |
>>> \ /
>>> | needle |
>>>>To: "Bryan Vandiver" <Bryan.Vandiver@eng.sun.com>
>>>>Cc: "spridgets list" <firstname.lastname@example.org>
>>>>Subject: Re: fuel gauge questions
>>>>X-MimeOLE: Produced By Microsoft MimeOLE V4.72.3110.3
>>>>If the two terminals on the back of the fuel gauge are marked with a "B"
>>>>battery, and a "T" for tank, then the two coils should be attached to
>>>>other in series. If there are no markings on the terminals on the back
>>>>the fuel gauge, then the two coils should be connected in parallel.
>>>>From: Bryan Vandiver <Bryan.Vandiver@Eng.Sun.COM>
>>>>To: email@example.com <firstname.lastname@example.org>
>>>>Date: Monday, August 09, 1999 6:43 PM
>>>>Subject: fuel gauge questions
>>>>>Does anyone have information on the internal wiring of the bugeye fuel
>>>>>My Gauge wasn't working at all, so I thought I'd open it up to find out
>>>>>There are two small 'coils' locate on either side of the needle assembly
>>>>>the gauge, but the 'hair fine' wires that were soldered to the needle
>>>>>have been broken off. Apparently a previous owner had unscrewed the coil
>>>>>assmblies from the back of the case, and in the process the coils
>>>>>breaking off the wires. the coils still look OK, and it looks like a
>>>>>matter to resolder them, unfortunately I can tell which wire goes where.
>>>>>assume the two coils were attached to each other, but all I see is two