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Fuel gauge wiring diagram needed for 156 jtd

Further to this post a couple of days ago i now need a wiring diagram for the fuel gauge to sender as the wires do not seem to bear any resemblance to the wires at the gauge block.
This is the original post.....


"Hello
I have a 2004 156 1.9jtd and the fuel gauge is not working. What happens is when you turn the ignition on the gauge needle moves slightly and the orange light comes on then goes off then after 40 seconds (this time remains constant ) the gauge goes right over to the extreme full end of the scale. Then when you turn the ignition off the gauge stays full for another 15 seconds (again this does not change) and then goes off.
I have tried another fuel gauge off another car and that did not work ,I have looked for the wiring earthing out as much as i can but if it was a straight forward earthing problem the gauge needle would jump to full straight away without the delay wouldnt it?
By the way the fuel light appears to work when it should."

The gauge does the same thing even with the sender wires at the tank disconnected so obviously not the tank sender , the time it takes the needle to go across the dial and back are strange and the delays are allways the same
Got me beat this one
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What was the age of the car that you tried the replacement gauge from? as the wiring an eletronics changed overtime (with the introduction of the facelift). The fuel gauge is not a simple analogue controller, the signal from the sender is a PWM digital signal which is then converted by a small chip in the gauge to value displayed.

However it is not as simple as that, it is the gauge that smooths out the fluctuations of the readings (as the car goes up/down hill/round corners) therefore it does perform quite a few smoothing calculations.

The behaviour you're seeing is the controller starting up (and I presume waiting for a valid signal) and then the 15 seconds at the end is the controller shutting down (the gauge has a "always on" live feed too - mainly for the clock).


Have you tried taking apart you guage and eyeballing the circuit?

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The gauge was from a 2000 156 so probably that wouldnt work anyway ,Judging by the behavior of the gauge it must be the instrument itself as the sender is disconnected and it still behaves the same way and i can find no wiring faults.
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help going mad

Well tried a brand new set of gauges for this car today exactly the same!!!!!!!!!!!!!!!
obviously not the gauges and as it does the same routine of waiting 40 seconds and then going to max on the gauge even with the tank sender disconnected and then 15 seconds after switching the ignition off before going back to empty the problem must lie somewhere inbetween tank and gauge. Normally i would have said it was the wires earthing out but it is the delay thing that boggles my mind!
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Quote:
Originally Posted by alfaaddicted View Post
Well tried a brand new set of gauges for this car today exactly the same!!!!!!!!!!!!!!!
obviously not the gauges and as it does the same routine of waiting 40 seconds and then going to max on the gauge even with the tank sender disconnected and then 15 seconds after switching the ignition off before going back to empty the problem must lie somewhere inbetween tank and gauge. Normally i would have said it was the wires earthing out but it is the delay thing that boggles my mind!
Did you not read my post? the delay at the beginning and the end is done purely by the gauge itself, not the signal (as you found out when you completely disconnected it)
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Originally Posted by 156Chris View Post
Did you not read my post? the delay at the beginning and the end is done purely by the gauge itself, not the signal (as you found out when you completely disconnected it)
yes i did read your reply thanks , but no point in taking the gauge to bits to inspect when a brand new gauge acts the same.

the problem obviously must be in the wiring twixt gauge and sender unless there is another item inbetween also the wiring colours at the sender and the gauge are different colours just to add to the fun
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Fuel gauge fixed ,woo hoo

Further to my previous post


"Hello
I have a 2004 156 1.9jtd and the fuel gauge is not working. What happens is when you turn the ignition on the gauge needle moves slightly and the orange light comes on then goes off then after 40 seconds (this time remains constant ) the gauge goes right over to the extreme full end of the scale. Then when you turn the ignition off the gauge stays full for another 15 seconds (again this does not change) and then goes off.
I have tried another fuel gauge off another car and that did not work ,I have looked for the wiring earthing out as much as i can but if it was a straight forward earthing problem the gauge needle would jump to full straight away without the delay wouldnt it?
By the way the fuel light appears to work when it should."

The gauge does the same thing even with the sender wires at the tank disconnected so obviously not the tank sender , the time it takes the needle to go across the dial and back are strange and the delays are allways the same
Got me beat this one

NOW CURED !!
All the problem was ,is that one of the block of connectors on the back of the speedo had come adrift !!
Plugged back in and all was restored to normal
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