VDO fuel gauge (zetec) reading full when empty
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Any suggestions about what I may be doing wrong with my fuel gauge/sender? - Both are VDO units, but when ignition is switched on gauge reads full when empty and when I move the float up gauge moves to empty.
- Stratosboy
- Second Gear
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no, it can only be fitted one way from top of tank.
- Stratosboy
- Second Gear
- Posts: 136
- Joined: 28 Dec 2007
tried swapping wires round, makes no difference and connector on back of gauge is a plug so can only go on one way. Definitely right plug on loom. Both gauge and sender unit are new VDO matched units.
??
??
- Stratosboy
- Second Gear
- Posts: 136
- Joined: 28 Dec 2007
If inside the sender, the device is a slider over a resistance wire, it may be that the wrong end of the resistance has been connected to the output wire.
But it looks as if your only real recourse is to complain to the seller.
'''''''''''''
There are many different VDO senders.
http://www.vdo-gauges.com/fluid-level-s ... ender.html
But it looks as if your only real recourse is to complain to the seller.
'''''''''''''
There are many different VDO senders.
http://www.vdo-gauges.com/fluid-level-s ... ender.html
Bill Williams
36/6725 S3 Coupe OGU108E Yellow over Black.
36/6725 S3 Coupe OGU108E Yellow over Black.
- billwill
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a coiled resistor behaves just like any resistor, and is not sensitive to current direction : when the resistor is low (slider next to the end connected to the other terminal or ground if grounded) a large current goes through, when the resistor is high a small current goes through. Then this current is used to move the needle of a gauge, and when assembling the two one must make sure that, say, the low fuel corresponds to the current level that gives a low fuel on the gauge.
For accuracy, there is also the question of absolute resistance values (impedance expected by the gauge for the whole range) - in case of mismatch tricks may be played in some instances by adding an external resistance or two, but it is not often easy to get a fully accurate reading then.
If possible I try to do a test with the actual components and circuit (gauge included) for both empty and full levels.
For accuracy, there is also the question of absolute resistance values (impedance expected by the gauge for the whole range) - in case of mismatch tricks may be played in some instances by adding an external resistance or two, but it is not often easy to get a fully accurate reading then.
If possible I try to do a test with the actual components and circuit (gauge included) for both empty and full levels.
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nmauduit - Coveted Fifth Gear
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>a coiled resistor behaves just like any resistor, and is not sensitive to current direction
When I said wrong end of the resistor, I was not considering direction of current flow, but the position of the sensor arm.
Connecting to the other end would reverse the full/empty resistance characteristics
eg if it was 0 ohms empty and 140 ohms full
it would now be
140 ohms full and 0 ohms empty.
Howver since VDO make sensors both ways (see that link I gave above) it is far, far more likely that the OP does not have a matched pair of gauge and sensor. i.e that the supplier sent the wrong bits.
When I said wrong end of the resistor, I was not considering direction of current flow, but the position of the sensor arm.
Connecting to the other end would reverse the full/empty resistance characteristics
eg if it was 0 ohms empty and 140 ohms full
it would now be
140 ohms full and 0 ohms empty.
Howver since VDO make sensors both ways (see that link I gave above) it is far, far more likely that the OP does not have a matched pair of gauge and sensor. i.e that the supplier sent the wrong bits.
Bill Williams
36/6725 S3 Coupe OGU108E Yellow over Black.
36/6725 S3 Coupe OGU108E Yellow over Black.
- billwill
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- Joined: 19 Apr 2008
billwill wrote:When I said wrong end of the resistor, I was not considering direction of current flow, but the position of the sensor arm.
it was said (post 3) that the sensor/resistor cannot be turned upside down - that would go in the good direction, while necessitating float arm bending
billwill wrote:Connecting to the other end would reverse the full/empty resistance characteristics
eg if it was 0 ohms empty and 140 ohms full
it would now be
140 ohms full and 0 ohms empty.
That would require a 3 terminal (potentiometric) coiled resistor (switching from say, bottom/middle to middle/top connections) - I have never seen such a sensor, though it possibly could be modified (but I personally would be reluctant to do it, since it is inside the tank and not pleasant to do again in case the hack fails prematurely)
billwill wrote:Howver since VDO make sensors both ways (see that link I gave above) it is far, far more likely that the OP does not have a matched pair of gauge and sensor. i.e that the supplier sent the wrong bits.
yes, it is my guess as well : the gauge end is where I would look into (making sure the expected impedance for "low fuel" and "high fuel" levels are matched to the sensor).
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nmauduit - Coveted Fifth Gear
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