TR Rob Posted February 2 Report Share Posted February 2 Set off, for a little run out in TR3A today, fuel gauge showed half full. After a few miles noticed fuel gauge was showing full, not only full, but it looked like it was against the stop. Stopped at petrol station and on turning engine off fuel gauge swung to empty. On starting engine after putting in fuel gauge showed about three quarter full, but later in journey it showed full, on the stop again ! Anyone else had a similar problem, could it be the tank sender or the gauge, any pointers would be helpful. Quote Link to post Share on other sites
RobH Posted February 2 Report Share Posted February 2 (edited) It could be the tank sender, or the connection to it, or even something inside the gauge. The '3A uses a balanced-gauge system where the gauge has two coils. One is connected to supply and earth to pull the needle towards 'full' and the other is connected from supply to the tank sender and pulls the needle towards 'empty' . A break somewhere on that side or a bad connection on the sender 'wiper' will cause this. It's done that way so the system works without the need for a voltage stabiliser, since changes in the voltage apply equally to both sides and are balanced out. This is from the 'dark side' but explains it well: http://www.mgaguru.com/mgtech/electric/fg_01.htm Edited February 2 by RobH Quote Link to post Share on other sites
Lebro Posted February 2 Report Share Posted February 2 Beat me to it. Symptoms suggest open circuit between tank sender, & "T" terminal on gauge. 1st check when in fault mode (full tank showing) would be to ground the wire going to the sender at the sender. Gauge should go to empty. Bob Quote Link to post Share on other sites
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