Hi everyone.

My old man has a Fiat Marea Weekend td100 (I'm pretty sure it's a 2000 model) with a strange fuel guage issue.

The guage always shows the tank as full even with the ignition turned off (as far as I know it should return to zero with the ignition off). If the car is left for more than a couple of days the battery drains.

He's fitted a new sender unit and a new battery but still can't get to the bottom of the problem and the local Fiat dealer is far from helpful.

I've had a look through the forum and can't see anybody with the same issue so I'm hoping someone may be able to point me in the right direction.

Hi,

Sounds like a short in the wiring to me.

The fuel tank sender is a fairly simple variable resistor which changes value as the float moves up or down. That 'value' is then carried to the gauge and the level is displayed accordingly.

Unfortunately I am not sure which way it is wired, i.e. I do not know if the gauge in the live or earth side of the wiring. I would have thought it is more likely to be in the live side with the stabilised power feed through the gauge to the sender then down to earth but Italians have some strange ideas about how to do things sometimes.

I will try to find time to look at the wiring diagrams in my Bravo/Brava manual over the next day or so and see if I can shed any more light on the subject.

In the meantime if you need it sorted faster any half decent auto electrician should be able to resolve the problem.

disconnect the tank sender unit at the tank and see if the gauge moves. given that its staying up with the ignition off, its quite likely then that the gauge needle is stuck in the cluster, in which case you could dismantle it to find out why - sometimes a piece of dust or dirt can jam the gauge mechanism. just remove the cluster (small allen key needed) and pull the front cover off the cluster (its held on with clips) and try moving the needle up and down with your finger. the needle should fall back to the zero position itself.
the tank sender itself is earthed. you could try connecting a small bulb (12V, 5W or 10W) across the contacts at the sender connector to see that the gauge is moving up and down correctly. To fix the battery drain issue - is there any aftermarket stuff installed - like a radio or alarm ?. try disconnecting these first. If still draining then switch off the roof light (stop it coming on with the doors open), get a multimeter, put it on the 200mA current range and disconnect the battery earth lead. connect the positive meter lead to the battery earth clamp or somewhere on the body, and get someone to hold the negative meter lead onto the battery earth (negative -) pole. note the readings, should be a few mA at most, depending on if there is an alarm fitted. If any higher, remove fuses one by one and note if the readings drop.