Triumph Herald 1200 Petrol Gauge Doing It's Own Thing

[Shiv K P]

Hello all, I filled my petrol tank to full yesterday and today as I was driving back from church, it randomly and suddenly from showing full, showed half tank. 

Can anyone show any light on the matter? I highly doubt it's used that much petrol within the space of doing about a five or six mile journey and that suddenly too.

Thanks! 

[Colin Lindsay]

Provided you did fill the tank to full - prices are way up these days!! - and you don't have a leak in the pipes then it's either going to be the sender, or the gauge electrics.

The sender ( if untouched so it hasn't been bent) may have developed a leak in the float, so it's now full of fuel and heavier than it should be. That may explain the sudden dip in the float height and correspondingly the reading at the gauge. You may need to remove it from the tank, when the level has definitely dropped below the sender outlet, and check. Obviously - be careful with the fuel fumes and disconnect the battery first. You can get replacement floats if required.

If it's the gauge... check that your voltage stabiliser on the rear of the speedo isn't playing up; if these fail they can show a full gauge as all the power goes straight to the gauge and the needle moves fully to the right, thereby giving a false sense of fuel reserve, and if it starts working again can then drop alarmingly, but they can also show an inaccurate reading too. They're only a bi-metallic strip so are affected by high temperatures. You might consider a modern electronic version, relatively easy to fit and more accurate..

[68vitesse]

If you remove the sender unit to gauge wire and short it to ground should that give a full reading on the gauge?. If it does this would indicate that the sender isn't at fault. if the reading on the gauge stays the same gauge or voltage stabilizer fault, full reading tank sender unit fault.

Leastwise thats how I think it would work on my Vitesse.

Regards

Paul.

 

[johny]

just to clarify a typo slip in the first part there Paul: As you said later, if the sender wire is put to earth and the gauge reading goes to full then the problem is with the sender...