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<title>Troubleshooting TR3A fuel gauge</title>
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<p dir="LTR"><span lang="en-ca"><font face="Calibri">Hello:</font></span></p>
<p dir="LTR"><span lang="en-ca"><font face="Calibri">I’ve been troubleshooting the</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"> <font face="Calibri">fuel gauge on my TR3A</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"> <font face="Calibri">because it has not been providing an accurate indication</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"> <font face="Calibri">(or even</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"><font face="Calibri"> a reasonable approximation)</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"> <font face="Calibri">of the fuel level in my tank.</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"><font face="Calibri"></font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"> </span></p>
<p dir="LTR"><span lang="en-ca"><font face="Calibri">I referred to a number of documents and old posts about how to troubleshoot and calibrate the fuel</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"><font face="Calibri"> gauge and sending unit (e.g.,</font></span><span lang="en-ca"> </span><a href="https://www.triumphexp.com/forum/tr2-and-tr3-forum.6/faulty-fuel-gauge-57-tr-3.1244960/"><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"><u><font color="#0563C1" face="Calibri">https://www.triumphexp.com/forum/tr2-and-tr3-forum.6/faulty-fuel-gauge-57-tr-3.1244960/</font></u></span><span lang="en-ca"></span></a><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"><font face="Calibri"> and</font></span><span lang="en-ca"> </span><a href="http://mgaguru.com/mgtech/electric/fg_01.htm"><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"><u><font color="#0563C1" face="Calibri">http://mgaguru.com/mgtech/electric/fg_01.htm</font></u></span><span lang="en-ca"></span></a><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"><font face="Calibri">).</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"></span></p>
<p dir="LTR"><span lang="en-ca"><font face="Calibri">I</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"> <font face="Calibri">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</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"> <font face="Calibri">didn’t stay the same even when I held the float at one level. I then checked to ensure that the grounds were good (</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"><font face="Calibri">they</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"><font face="Calibri"> were). Before</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"> <font face="Calibri">concludin</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"><font face="Calibri">g that the</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"> <font face="Calibri">sending unit</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"><font face="Calibri"> was flakey</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"><font face="Calibri">, I tho</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"><font face="Calibri">ught I’d</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"> <font face="Calibri">better ensure that</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"><font face="Calibri"> I was getting good power to the unit.</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"> </span></p>
<p dir="LTR"><span lang="en-ca"><font face="Calibri">That’s where things got weird.</font></span></p>
<p dir="LTR"><span lang="en-ca"><font face="Calibri">- </font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"> <font face="Calibri">I read 7.6V between the sending unit and ground</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"><font face="Calibri">.</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"> </span></p>
<p dir="LTR"><span lang="en-ca"><font face="Calibri">- </font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"> <font face="Calibri">I</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"> <font face="Calibri">read</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"><font face="Calibri"></font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"> <font face="Calibri">7.65V</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"><font face="Calibri"> between the T terminal of the fuel gauge</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"> <font face="Calibri">(which connects to the fuel tank sendin</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"><font face="Calibri">g unit)</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"> <font face="Calibri">and ground.</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"><font face="Calibri"></font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"> <font face="Calibri">However, this reading was erratic; the value would change to, say 4V.</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"></span></p>
<p dir="LTR"><span lang="en-ca"><font face="Calibri">- </font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"> <font face="Calibri">I</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"> <font face="Calibri">read 10.6V</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"> <font face="Calibri">at the B termin</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"><font face="Calibri">al of the fuel gauge</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"></span></p>
<p dir="LTR"><span lang="en-ca"><font face="Calibri">- </font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"> <font face="Calibri">I read</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"> <font face="Calibri">10.9V at the A4 terminal</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"><font face="Calibri"> of the fuse box</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"><font face="Calibri">.</font></span></p>
<p dir="LTR"><span lang="en-ca"><font face="Calibri">- </font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"> <font face="Calibri">I read 11.9V</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"> <font face="Calibri">at the A2 terminal of the fuse box.</font></span></p>
<p dir="LTR"><span lang="en-ca"><font face="Calibri">- </font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"> <font face="Calibri">I read 12.5v between the terminals of the battery.</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"></span></p>
<p dir="LTR"><span lang="en-ca"><font face="Calibri">I’m a bit baffled</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"><font face="Calibri">. I expected that I’d see about 12V at all points.</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"> <font face="Calibri">Even if the</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"> <font face="Calibri">fuel</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"> <font face="Calibri">gauge was bad, I would have expected</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"> <font face="Calibri">to see</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"> <font face="Calibri">the same voltage at the battery, A2, A4, and the B terminal of the gauge</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"><font face="Calibri">. As it is, I’m seeing a drop of about 2V among them.</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"></span></p>
<p dir="LTR"><span lang="en-ca"><font face="Calibri">What might be causing the v</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"><font face="Calibri">oltage drops that I’m seeing? Could it be as simple as a broken fuel gauge? If so, how could I test that?</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"></span></p>
<p dir="LTR"><span lang="en-ca"><font face="Calibri">Moss lists the fuel gauge as NLA. Does anyone know of ano</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"><font face="Calibri">ther source?</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"></span></p>
<p dir="LTR"><span lang="en-ca"><font face="Calibri">BTW, w</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"><font face="Calibri">hen I</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"> <font face="Calibri">switch</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"><font face="Calibri">ed</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"><font face="Calibri"> my generator for an alternator</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"><font face="Calibri"> years ago</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"><font face="Calibri">,</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"> <font face="Calibri">I</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"> <font face="Calibri">eliminated the</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"> <font face="Calibri">control box</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"><font face="Calibri"> (regulator)</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"><font face="Calibri">.</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"> </span></p>
<p dir="LTR"><span lang="en-ca"><font face="Calibri">Thanks in advance.</font></span></p>
<p dir="LTR"><span lang="en-ca"><font face="Calibri">Dave MacKay</font></span></p>
<p dir="LTR"><span lang="en-ca"><font face="Calibri">TR3A s/n 68639L</font></span></p>
<p dir="LTR"><span lang="en-ca"><font face="Calibri">near Toronto, Canada</font></span><span lang="en-ca"></span><span lang="en-ca"></span><span lang="en-ca"></span></p>
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