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Troubleshooting TR3A fuel gauge
Hello:
I=E2=80=99ve been troubleshooting the fuel gauge on my TR3A because it has =
not been
providing an accurate indication (or even a reasonable approximation) of
the fuel level in my tank.
I referred to a number of documents and old posts about how to troubleshoot
and calibrate the fuel gauge and sending unit (e.g.,
*https://www.triumphexp.com/forum/tr2-and-tr3-forum.6/faulty-fuel-gauge-57-=
tr-3.1244960/*
<https://www.triumphexp.com/forum/tr2-and-tr3-forum.6/faulty-fuel-gauge-57-=
tr-3.1244960/>
and *http://mgaguru.com/mgtech/electric/fg_01.htm*
<http://mgaguru.com/mgtech/electric/fg_01.htm>).
I started by looping a clothes hanger around the float in the tank and
reading how many ohms I saw at different levels. What I found was that the
reading fluctuated --- it didn=E2=80=99t stay the same even when I held the=
float
at one level. I then checked to ensure that the grounds were good (they
were). Before concluding that the sending unit was flakey, I thought I=E2=
=80=99d better
ensure that I was getting good power to the unit.
That=E2=80=99s where things got weird.
- I read 7.6V between the sending unit and ground.
- I read 7.65V between the T terminal of the fuel gauge (which
connects to the fuel tank sending unit) and ground. However, this reading
was erratic; the value would change to, say 4V.
- I read 10.6V at the B terminal of the fuel gauge
- I read 10.9V at the A4 terminal of the fuse box.
- I read 11.9V at the A2 terminal of the fuse box.
- I read 12.5v between the terminals of the battery.
I=E2=80=99m a bit baffled. I expected that I=E2=80=99d see about 12V at all=
points. Even if
the fuel gauge was bad, I would have expected to see the same voltage at
the battery, A2, A4, and the B terminal of the gauge. As it is, I=E2=80=99m=
seeing
a drop of about 2V among them.
What might be causing the voltage drops that I=E2=80=99m seeing? Could it b=
e as
simple as a broken fuel gauge? If so, how could I test that?
Moss lists the fuel gauge as NLA. Does anyone know of another source?
BTW, when I switched my generator for an alternator years ago, I eliminated
the control box (regulator).
Thanks in advance.
Dave MacKay
TR3A s/n 68639L
near Toronto, Canada
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<p dir=3D"LTR"><span lang=3D"en-ca"><font face=3D"Calibri">Hello:</font></s=
pan></p>
<p dir=3D"LTR"><span lang=3D"en-ca"><font face=3D"Calibri">I=E2=80=99ve bee=
n troubleshooting the</font></span><span lang=3D"en-ca"></span><span lang=
=3D"en-ca"></span><span lang=3D"en-ca"> <font face=3D"Calibri">fuel gauge o=
n my TR3A</font></span><span lang=3D"en-ca"></span><span lang=3D"en-ca"></s=
pan><span lang=3D"en-ca"> <font face=3D"Calibri">because it has not been pr=
oviding an accurate indication</font></span><span lang=3D"en-ca"></span><sp=
an lang=3D"en-ca"></span><span lang=3D"en-ca"> <font face=3D"Calibri">(or e=
ven</font></span><span lang=3D"en-ca"></span><span lang=3D"en-ca"></span><s=
pan lang=3D"en-ca"><font face=3D"Calibri"> a reasonable approximation)</fon=
t></span><span lang=3D"en-ca"></span><span lang=3D"en-ca"></span><span lang=
=3D"en-ca"> <font face=3D"Calibri">of the fuel level in my tank.</font></sp=
an><span lang=3D"en-ca"></span><span lang=3D"en-ca"></span><span lang=3D"en=
-ca"><font face=3D"Calibri"></font></span><span lang=3D"en-ca"></span><span=
lang=3D"en-ca"></span><span lang=3D"en-ca"> </span></p>
<p dir=3D"LTR"><span lang=3D"en-ca"><font face=3D"Calibri">I referred to a =
number of documents and old posts about how to troubleshoot and calibrate t=
he fuel</font></span><span lang=3D"en-ca"></span><span lang=3D"en-ca"></spa=
n><span lang=3D"en-ca"><font face=3D"Calibri"> gauge and sending unit (e.g.=
,</font></span><span lang=3D"en-ca"> </span><a href=3D"https://www.triumphe=
xp.com/forum/tr2-and-tr3-forum.6/faulty-fuel-gauge-57-tr-3.1244960/"><span =
lang=3D"en-ca"></span><span lang=3D"en-ca"></span><span lang=3D"en-ca"><u><=
font color=3D"#0563C1" face=3D"Calibri">https://www.triumphexp.com/forum/tr=
2-and-tr3-forum.6/faulty-fuel-gauge-57-tr-3.1244960/</font></u></span><span=
lang=3D"en-ca"></span></a><span lang=3D"en-ca"></span><span lang=3D"en-ca"=
></span><span lang=3D"en-ca"><font face=3D"Calibri"> and</font></span><span=
lang=3D"en-ca"> </span><a href=3D"http://mgaguru.com/mgtech/electric/fg_01=
.htm"><span lang=3D"en-ca"></span><span lang=3D"en-ca"></span><span lang=3D=
"en-ca"><u><font color=3D"#0563C1" face=3D"Calibri">http://mgaguru.com/mgte=
ch/electric/fg_01.htm</font></u></span><span lang=3D"en-ca"></span></a><spa=
n lang=3D"en-ca"></span><span lang=3D"en-ca"></span><span lang=3D"en-ca"><f=
ont face=3D"Calibri">).</font></span><span lang=3D"en-ca"></span><span lang=
=3D"en-ca"></span><span lang=3D"en-ca"></span></p>
<p dir=3D"LTR"><span lang=3D"en-ca"><font face=3D"Calibri">I</font></span><=
span lang=3D"en-ca"></span><span lang=3D"en-ca"></span><span lang=3D"en-ca"=
> <font face=3D"Calibri">started by looping a clothes hanger around the flo=
at in the tank and reading how many ohms I saw at different levels. What I =
found was that the reading fluctuated --- it</font></span><span lang=3D"en-=
ca"></span><span lang=3D"en-ca"></span><span lang=3D"en-ca"> <font face=3D"=
Calibri">didn=E2=80=99t stay the same even when I held the float at one lev=
el. I then checked to ensure that the grounds were good (</font></span><spa=
n lang=3D"en-ca"></span><span lang=3D"en-ca"></span><span lang=3D"en-ca"><f=
ont face=3D"Calibri">they</font></span><span lang=3D"en-ca"></span><span la=
ng=3D"en-ca"></span><span lang=3D"en-ca"><font face=3D"Calibri"> were). Bef=
ore</font></span><span lang=3D"en-ca"></span><span lang=3D"en-ca"></span><s=
pan lang=3D"en-ca"> <font face=3D"Calibri">concludin</font></span><span lan=
g=3D"en-ca"></span><span lang=3D"en-ca"></span><span lang=3D"en-ca"><font f=
ace=3D"Calibri">g that the</font></span><span lang=3D"en-ca"></span><span l=
ang=3D"en-ca"></span><span lang=3D"en-ca"> <font face=3D"Calibri">sending u=
nit</font></span><span lang=3D"en-ca"></span><span lang=3D"en-ca"></span><s=
pan lang=3D"en-ca"><font face=3D"Calibri"> was flakey</font></span><span la=
ng=3D"en-ca"></span><span lang=3D"en-ca"></span><span lang=3D"en-ca"><font =
face=3D"Calibri">, I tho</font></span><span lang=3D"en-ca"></span><span lan=
g=3D"en-ca"></span><span lang=3D"en-ca"><font face=3D"Calibri">ught I=E2=80=
=99d</font></span><span lang=3D"en-ca"></span><span lang=3D"en-ca"></span><=
span lang=3D"en-ca"> <font face=3D"Calibri">better ensure that</font></span=
><span lang=3D"en-ca"></span><span lang=3D"en-ca"></span><span lang=3D"en-c=
a"><font face=3D"Calibri"> I was getting good power to the unit.</font></sp=
an><span lang=3D"en-ca"></span><span lang=3D"en-ca"></span><span lang=3D"en=
-ca"> </span></p>
<p dir=3D"LTR"><span lang=3D"en-ca"><font face=3D"Calibri">That=E2=80=99s w=
here things got weird.</font></span></p>
<p dir=3D"LTR"><span lang=3D"en-ca"><font face=3D"Calibri">-=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0</font></span><span lang=3D"en-ca"></span><span lang=
=3D"en-ca"></span><span lang=3D"en-ca"></span><span lang=3D"en-ca"></span><=
span lang=3D"en-ca"> <font face=3D"Calibri">I read 7.6V between the sending=
unit and ground</font></span><span lang=3D"en-ca"></span><span lang=3D"en-=
ca"></span><span lang=3D"en-ca"><font face=3D"Calibri">.</font></span><span=
lang=3D"en-ca"></span><span lang=3D"en-ca"></span><span lang=3D"en-ca"> </=
span></p>
<p dir=3D"LTR"><span lang=3D"en-ca"><font face=3D"Calibri">-=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0</font></span><span lang=3D"en-ca"></span><span lang=
=3D"en-ca"></span><span lang=3D"en-ca"></span><span lang=3D"en-ca"> <font f=
ace=3D"Calibri">I</font></span><span lang=3D"en-ca"></span><span lang=3D"en=
-ca"></span><span lang=3D"en-ca"> <font face=3D"Calibri">read</font></span>=
<span lang=3D"en-ca"></span><span lang=3D"en-ca"></span><span lang=3D"en-ca=
"><font face=3D"Calibri"></font></span><span lang=3D"en-ca"></span><span la=
ng=3D"en-ca"></span><span lang=3D"en-ca"> <font face=3D"Calibri">7.65V</fon=
t></span><span lang=3D"en-ca"></span><span lang=3D"en-ca"></span><span lang=
=3D"en-ca"><font face=3D"Calibri"> between the T terminal of the fuel gauge=
</font></span><span lang=3D"en-ca"></span><span lang=3D"en-ca"></span><span=
lang=3D"en-ca"> <font face=3D"Calibri">(which connects to the fuel tank se=
ndin</font></span><span lang=3D"en-ca"></span><span lang=3D"en-ca"></span><=
span lang=3D"en-ca"><font face=3D"Calibri">g unit)</font></span><span lang=
=3D"en-ca"></span><span lang=3D"en-ca"></span><span lang=3D"en-ca"> <font f=
ace=3D"Calibri">and ground.</font></span><span lang=3D"en-ca"></span><span =
lang=3D"en-ca"></span><span lang=3D"en-ca"><font face=3D"Calibri"></font></=
span><span lang=3D"en-ca"></span><span lang=3D"en-ca"></span><span lang=3D"=
en-ca"> <font face=3D"Calibri">However, this reading was erratic; the value=
would change to, say 4V.</font></span><span lang=3D"en-ca"></span><span la=
ng=3D"en-ca"></span><span lang=3D"en-ca"></span></p>
<p dir=3D"LTR"><span lang=3D"en-ca"><font face=3D"Calibri">-=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0</font></span><span lang=3D"en-ca"></span><span lang=
=3D"en-ca"></span><span lang=3D"en-ca"></span><span lang=3D"en-ca"> <font f=
ace=3D"Calibri">I</font></span><span lang=3D"en-ca"></span><span lang=3D"en=
-ca"></span><span lang=3D"en-ca"> <font face=3D"Calibri">read 10.6V</font><=
/span><span lang=3D"en-ca"></span><span lang=3D"en-ca"></span><span lang=3D=
"en-ca"> <font face=3D"Calibri">at the B termin</font></span><span lang=3D"=
en-ca"></span><span lang=3D"en-ca"></span><span lang=3D"en-ca"><font face=
=3D"Calibri">al of the fuel gauge</font></span><span lang=3D"en-ca"></span>=
<span lang=3D"en-ca"></span><span lang=3D"en-ca"></span></p>
<p dir=3D"LTR"><span lang=3D"en-ca"><font face=3D"Calibri">-=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0</font></span><span lang=3D"en-ca"></span><span lang=
=3D"en-ca"></span><span lang=3D"en-ca"></span><span lang=3D"en-ca"> <font f=
ace=3D"Calibri">I read</font></span><span lang=3D"en-ca"></span><span lang=
=3D"en-ca"></span><span lang=3D"en-ca"> <font face=3D"Calibri">10.9V at the=
A4 terminal</font></span><span lang=3D"en-ca"></span><span lang=3D"en-ca">=
</span><span lang=3D"en-ca"><font face=3D"Calibri"> of the fuse box</font><=
/span><span lang=3D"en-ca"></span><span lang=3D"en-ca"></span><span lang=3D=
"en-ca"><font face=3D"Calibri">.</font></span></p>
<p dir=3D"LTR"><span lang=3D"en-ca"><font face=3D"Calibri">-=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0</font></span><span lang=3D"en-ca"></span><span lang=
=3D"en-ca"></span><span lang=3D"en-ca"></span><span lang=3D"en-ca"> <font f=
ace=3D"Calibri">I read 11.9V</font></span><span lang=3D"en-ca"></span><span=
lang=3D"en-ca"></span><span lang=3D"en-ca"> <font face=3D"Calibri">at the =
A2 terminal of the fuse box.</font></span></p>
<p dir=3D"LTR"><span lang=3D"en-ca"><font face=3D"Calibri">-=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0</font></span><span lang=3D"en-ca"></span><span lang=
=3D"en-ca"></span><span lang=3D"en-ca"></span><span lang=3D"en-ca"> <font f=
ace=3D"Calibri">I read 12.5v between the terminals of the battery.</font></=
span><span lang=3D"en-ca"></span><span lang=3D"en-ca"></span><span lang=3D"=
en-ca"></span></p>
<p dir=3D"LTR"><span lang=3D"en-ca"><font face=3D"Calibri">I=E2=80=99m a bi=
t baffled</font></span><span lang=3D"en-ca"></span><span lang=3D"en-ca"></s=
pan><span lang=3D"en-ca"><font face=3D"Calibri">. I expected that I=E2=80=
=99d see about 12V at all points.</font></span><span lang=3D"en-ca"></span>=
<span lang=3D"en-ca"></span><span lang=3D"en-ca"> <font face=3D"Calibri">Ev=
en if the</font></span><span lang=3D"en-ca"></span><span lang=3D"en-ca"></s=
pan><span lang=3D"en-ca"> <font face=3D"Calibri">fuel</font></span><span la=
ng=3D"en-ca"></span><span lang=3D"en-ca"></span><span lang=3D"en-ca"> <font=
face=3D"Calibri">gauge was bad, I would have expected</font></span><span l=
ang=3D"en-ca"></span><span lang=3D"en-ca"></span><span lang=3D"en-ca"> <fon=
t face=3D"Calibri">to see</font></span><span lang=3D"en-ca"></span><span la=
ng=3D"en-ca"></span><span lang=3D"en-ca"> <font face=3D"Calibri">the same v=
oltage at the battery, A2, A4, and the B terminal of the gauge</font></span=
><span lang=3D"en-ca"></span><span lang=3D"en-ca"></span><span lang=3D"en-c=
a"><font face=3D"Calibri">. As it is, I=E2=80=99m seeing a drop of about 2V=
among them.</font></span><span lang=3D"en-ca"></span><span lang=3D"en-ca">=
</span><span lang=3D"en-ca"></span></p>
<p dir=3D"LTR"><span lang=3D"en-ca"><font face=3D"Calibri">What might be ca=
using the v</font></span><span lang=3D"en-ca"></span><span lang=3D"en-ca"><=
/span><span lang=3D"en-ca"><font face=3D"Calibri">oltage drops that I=E2=80=
=99m seeing? Could it be as simple as a broken fuel gauge? If so, how could=
I test that?</font></span><span lang=3D"en-ca"></span><span lang=3D"en-ca"=
></span><span lang=3D"en-ca"></span></p>
<p dir=3D"LTR"><span lang=3D"en-ca"><font face=3D"Calibri">Moss lists the f=
uel gauge as NLA. Does anyone know of ano</font></span><span lang=3D"en-ca"=
></span><span lang=3D"en-ca"></span><span lang=3D"en-ca"><font face=3D"Cali=
bri">ther source?</font></span><span lang=3D"en-ca"></span><span lang=3D"en=
-ca"></span><span lang=3D"en-ca"></span></p>
<p dir=3D"LTR"><span lang=3D"en-ca"><font face=3D"Calibri">BTW, w</font></s=
pan><span lang=3D"en-ca"></span><span lang=3D"en-ca"></span><span lang=3D"e=
n-ca"><font face=3D"Calibri">hen I</font></span><span lang=3D"en-ca"></span=
><span lang=3D"en-ca"></span><span lang=3D"en-ca"> <font face=3D"Calibri">s=
witch</font></span><span lang=3D"en-ca"></span><span lang=3D"en-ca"></span>=
<span lang=3D"en-ca"><font face=3D"Calibri">ed</font></span><span lang=3D"e=
n-ca"></span><span lang=3D"en-ca"></span><span lang=3D"en-ca"><font face=3D=
"Calibri"> my generator for an alternator</font></span><span lang=3D"en-ca"=
></span><span lang=3D"en-ca"></span><span lang=3D"en-ca"><font face=3D"Cali=
bri"> years ago</font></span><span lang=3D"en-ca"></span><span lang=3D"en-c=
a"></span><span lang=3D"en-ca"><font face=3D"Calibri">,</font></span><span =
lang=3D"en-ca"></span><span lang=3D"en-ca"></span><span lang=3D"en-ca"> <fo=
nt face=3D"Calibri">I</font></span><span lang=3D"en-ca"></span><span lang=
=3D"en-ca"></span><span lang=3D"en-ca"> <font face=3D"Calibri">eliminated t=
he</font></span><span lang=3D"en-ca"></span><span lang=3D"en-ca"></span><sp=
an lang=3D"en-ca"> <font face=3D"Calibri">control box</font></span><span la=
ng=3D"en-ca"></span><span lang=3D"en-ca"></span><span lang=3D"en-ca"><font =
face=3D"Calibri"> (regulator)</font></span><span lang=3D"en-ca"></span><spa=
n lang=3D"en-ca"></span><span lang=3D"en-ca"><font face=3D"Calibri">.</font=
></span><span lang=3D"en-ca"></span><span lang=3D"en-ca"></span><span lang=
=3D"en-ca"> </span></p>
<p dir=3D"LTR"><span lang=3D"en-ca"><font face=3D"Calibri">Thanks in advanc=
e.</font></span></p>
<p dir=3D"LTR"><span lang=3D"en-ca"><font face=3D"Calibri">Dave MacKay</fon=
t></span></p>
<p dir=3D"LTR"><span lang=3D"en-ca"><font face=3D"Calibri">TR3A s/n 68639L<=
/font></span></p>
<p dir=3D"LTR"><span lang=3D"en-ca"><font face=3D"Calibri">near Toronto, Ca=
nada</font></span><span lang=3D"en-ca"></span><span lang=3D"en-ca"></span><=
span lang=3D"en-ca"></span></p>
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