[ryker]

Would the voltage regulator affect just one gauge?

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[ds968]

That would be my question also. All the other gauges work perfectly as they should, with the sole exception of the fuel one . And although in the six speed the fuel gauge is off also ( the needle is under the full line by approx its own width on any fill up, it stays there for a long time and moves down very slowly getting to the middle only around 300 mi., then the bottom half it moves at twice the speed toward empty ) , the gauge in the tip is possessed ! I filled it up today and drove 60 miles - the needle is half way between the 3/4 bar and the 1/2 bar !! Simply nuts !

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[Bulti]

[quote name='ryker' timestamp='1386533380' post='153411']

Bulti, it's certainly worth trying your fix. Would you mind posting photo? Thanks

[/quote]



   



This is a picture taken from the underside of the fuel sender. The metal thing that touches the inside wall was very gently moved to the side a bit, so I could wipe off the 'film' (parly left visible) that was deposited there by the fuel over the years.



Could the metal thingy act as a ground? I actually have no clue, but it costs nothing and it's worth a shot. It seemed to have worked in my case, the fuel gauge stopped dancing around.



Joel, maybe you could shed some light onto this?

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[polliviere]

A few years ago I was involved with an audi tech class at the audi training center and the question of how the fuel usage did not seem to track actual usage came up. The answer was simple, the usage was designed to act that way. It seems that the average driving masses would get very upset when the gauge started to move from full right after filling up. In their mind this ment that the car was guzzling gas. The solution was to make the gauge slow to react at the top of it's travel and then catch up as it gets down in the half to quarter range. If you think about it you will see this happen in just about every car you drive.

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[polliviere]

Sorry for off topic but I just noticed the message "warn status" at the bottom of my last post. I have no idea what that is about, anyone know?

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[Bulti]

Polli, that would certainly explain the gauge's behavior, I never had a car without those symptoms anyway.



Guess when that meter's full, you're out of here? Or maybe shot?

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[JWahlsten]

Sorry guys away for a couple of days.



The grounds underneath the dash and behind the cluster are what I was referring to...Yes, all the other gauges will work correctly, but for some reason the fuel gauge is sensitive to the grounds and power. Seems odd, but try an adjustable voltage regulator after cleaning the grounds. You'll have a full tank and brighter lights...



Philippe,

I am not certain of the functions of the different parts of the sender.

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[Bulti]

Assuming the reflective surface of the instrument cluster is still in good condition.



Is the gauge itself adjustable?

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[ryker]

JWhalsten, very interesting because my dash lights are very dull in my green car. It is a huge difference from my other cars. I'll add "check the grounds" to my to-do list!

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[94SilverCab]

[quote name='polliviere' timestamp='1386616086' post='153436']

Sorry for off topic but I just noticed the message "warn status" at the bottom of my last post. I have no idea what that is about, anyone know?

[/quote]





That is there to inform you if you have been warned by a moderator. It has always been there and your level is -0-.



Jay

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[williamoss]

I just found this thread as I was looking for another. My gauge has never gone to max fill line, except when unit the float was out of the car, and we hooked up the wires independently. The gauge moved up to max line. I have replaced the float unit in the tank 3 times and it never works properly. I also zero out the trip odometer each fill up and when I have driven approx. 180-220 miles I fill it up. By that time the gauge is somewhere near the 1/4 of tank mark. But if it will move up to close to the fill line is anyone's guess. 

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[type968]

I just found this thread as I was looking for another. My gauge has never gone to max fill line, except when unit the float was out of the car, and we hooked up the wires independently. The gauge moved up to max line. I have replaced the float unit in the tank 3 times and it never works properly. I also zero out the trip odometer each fill up and when I have driven approx. 180-220 miles I fill it up. By that time the gauge is somewhere near the 1/4 of tank mark. But if it will move up to close to the fill line is anyone's guess. 

  

I never looked into mine, but from all my voodoo internet reading, it is your sender and the grounds most of the time on the trunk side of things.  I thought the gauge was resistance based, so the lower the drop the higher the resistance.  I thought I read of people calibrating the gauge side, but that was just masking the original problem.

 

So I think most people either replaced the sender, or took apart, cleaned, re-solders spades, cleaned grounds etc, and got the sender to send the correct resistance for full again.

 

Remember, any corrosion, etc that can cause greater resistance acts like a low fuel level signal to the car.

 

Fill the car with gas, pull the sender plug and measure the sender terminals (and remember you are messing with electricity and fuel here)

 

This is from a 944, so not sure what 968 should read:

Model Year 1985.5-1995 Level Resistance (Ohms)

RESERVE 63.2

1/4  42.2

1/2 21.2

3/4 8.6

FULL (1/1) 2.8

 

http://www.clarks-garage.com/shop-manual/elect-13.htm

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[MCL968]

I cleaned the contacts on the back of the instrument cluster, now it goes up to almost full.

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[Bulti]

On my car it took a new fuel level sender AND a good cleaning of the grounds on the back of the cluster. The little copper nuts have to come off and be cleaned. Cleaning the sender helped with any potential erratic behaviour of the gauge but in the end a new one was the only decent fix. Whit the tank topped up and clean grounds, my gauge goes even slightly above the top white mark.


Fiddling with the gauge itself would be indeed just masking the real cause of the problem. Fix it the correct way and be done with it.

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