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  #1  
Old June 9th, 2006, 10:43 PM
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bouncing fuel gauge

replaced gauges this week (with aftermarket)and the fuel gauge bounces like crazy(i read this was common).only stays still if the 90 is not moving.anyone know anyway to fix or maybe minimize the bouncing.talked to tech support this morning and they said its normal and the did not know of anything to help
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  #2  
Old June 9th, 2006, 10:59 PM
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What brand gauge is it? Sounds like it's not damped, so the needle is going to bounce along with the sender. As the fuel splashes around in the tank, the sender is constantly bouncing up and down, and the meter follows along. Most factory gauges have some type of dampening to slow down the movement and reduce all the bouncing at the needle, though the signal is still all bouncy.

-Hans
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  #3  
Old June 9th, 2006, 11:10 PM
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My factory bounces. When I go arond a left turn (full tank) Right turn (empty)
Ive just learned to live with it as a Defender thing.
Michael
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  #4  
Old June 9th, 2006, 11:12 PM
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The factory ones move.... but I have also seen the bouncing as well on undampned gauges. Can be almost unreadable if you are on a rough road. Looking up solutions now, found a few.

First one, use a chemical condensor in the wiring harness. (interesting, will have to ask a buddy of mine about this one)
http://www.clubcobra.com/t56124.html

Another option is to use a small dab of heavy grease on the pivot point in the gauge like some factory ones use..... not something I'd recommend if the gauge wasn't designed for it.

-Hans
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  #5  
Old June 9th, 2006, 11:28 PM
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hans is right- it bounces just going down the road.my factory moved but nothing like this.unreadable until stopped.hans i put in classic instruments gauges.i think the web site says all there gauges are dampened???i cant tell. the tach is very smooth.

Follow-up Post:

hans do you know where i can get that?radio shack or someplace?
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  #6  
Old June 9th, 2006, 11:46 PM
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The only other thing I can dig up is that bouncy gauges is also sometimes a sign of poor connections or maybe a sender that is starting to wear at the rheostat causing a bad signal. How bouncy was it before you changed it? Did it only move around in turns, or driving down a straight road?

It's definitely NOT a crappy gauge in there, I've heard nothing but good about the Classic gauges lineup. I'm not sure I'd suggest experimenting with extra stuff wired on the outside with a gauge that nice either.

My thinking is maybe they aren't used to dealing with off-road type people, and that it's not as much of an issue with street-rods. Maybe give Classic another call, let them know that you are using it on an off-road truck, and that the fuel tank isn't baffled at all, and ask if they offer anything with a slow movement to the needle?

I have a buddy of mine that is an electical engineer, but I won't see him until Sunday when he is back at work. I won't be able to ask him about it until then.

Follow-up Post:

One more thought.

How much gas in the tank? I know that because of the geometry of the float on the sender, the last quarter of a tank or so causes a lot more fluctuation in the resistance of the sender. But it is much smoother when you have more than half a tank or so. So if your tank is low, the gauge will bounce around a LOT more than if the tank is close to full.

-Hans
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  #7  
Old June 10th, 2006, 01:32 AM
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the stock fuel gauge was fine,i dont even recall it moving, maybe on turns.the gas tank has at least 3/4 full if not more.i did let the tech know there was no baffels
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  #8  
Old June 10th, 2006, 01:15 PM
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The electrical solution does not work, adding a capacitor of the mentioned values in the reference with the associated sender resistance has not any noticeable effect minimizing the needle bouncing.

I'm replacing my 90 gauge set with VDO stuff + an electronic LR speedo and It seems the speedo has a fuel gauge electrical dampening on it, see the pictures.
I didn't installed the system yet but i think is the way to go
Pat
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  #9  
Old June 10th, 2006, 05:57 PM
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I've been talking to a few people, and have gotten the suggestion of a capacitor from a few of them, but they've all said that the uF value needed will vary and too low of a value will have little effect. I'm trying to get some second opinions on that, and to source some variable capacitors that will allow for knob tuning of the dampening rate.

-Hans
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  #10  
Old June 10th, 2006, 07:01 PM
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did you see the link on the clubcobra site article hans posted.there was a link to centroidproducts.com anyone see a reason that would not work?
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  #11  
Old June 10th, 2006, 09:20 PM
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That sender would probably work like a charm, they do flat out advertise they can build dampened senders. Plus the fact they can custom build and calibrate it for you as well. If the mounting methods they have are compatible, it should be a case of just sending them the specs and dropping in the new sender when it arrives.

It also functions using a totally different principle, so most likely it would also read consistant from top to bottom unlike a float on an arm that changes rate. Mine with the stock setup, the first half tank lasts 125 miles, the 2nd half of the tank lasts 30 miles. Not to mention that it has no moving parts to wear out over time, another bonus. I just worry about the price on those, but I'm very interested in one for myself too.

-Hans

Follow-up Post:

Hmmm, actually..... I don't know if those senders will work. They don't seem to offer a compatible mounting flange at all. But maybe other companies offer the same type that will fit.

-Hans
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  #12  
Old June 10th, 2006, 09:28 PM
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Quote:
Originally Posted by Hans
I've been talking to a few people, and have gotten the suggestion of a capacitor from a few of them, but they've all said that the uF value needed will vary and too low of a value will have little effect. I'm trying to get some second opinions on that, and to source some variable capacitors that will allow for knob tuning of the dampening rate.

-Hans
In my opinion there's no practical C value able to make that thing work; the associated resistance value is always too low.
Let say we got 1000uF the capacitor and 100 ohms the resistor, that gives you a T= 1000uF x100 ohms = 0.1 S
that means something like the needle is going to take 0.1 s to get 70% from its final position after a car movement.
0.1 sec is way too low.
T should be something like 5-7 sec. We can get that if the capacitor is 70.000 uF(pretty big) but when the tank gets close to full the resistance goes close to 40 ohms or less and that means we'd need even a bigger capacitor...
Yes, we can still use an audio cap 1F or bigger,sure they work, but I don't know where are you going to install it behind the dashboard after paying $100 or thing like that for one of those...

About variable capacitors on these values; they definitely do not exist.


Pat
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  #13  
Old June 10th, 2006, 11:07 PM
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Gotcha. Theory ok, practical application no good on the capacitors. That leaves something like a microprocessor that samples and smooths the rate, and that is well past the garage tinker realm of possibility.

The capacitive sending units with built in dampening sure would be a great option, but I'm not 100% sure that we can get them so they will mount on the tank easily. I've never taken one apart yet on a D-90 so I'll have to dig my manual out when I get home from work and see how the sender actually mounts in the tank and try to see how easy it would be to adapt them in.

-Hans

Follow-up Post:

Well, it's all a moot point about swapping the senders it looks like. The sender is an integrated part of the fuel pump, so changing the type of sender or the resistance curves is a moot point anyways.

-Hans
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  #14  
Old June 11th, 2006, 12:09 AM
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John Robison has a solution to the bouncing fuel gauge . I can't remember how he solved the problem but it involves the fuel pump. I hope he reads this post so he can offer his solution..
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  #15  
Old June 11th, 2006, 11:08 PM
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i was curious-i read that some speedo shops can switch out the face of you orginal speedo with a new aftermarket guts?if so could you do the same with the fuel gauge?
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  #16  
Old June 11th, 2006, 11:50 PM
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Matt, sorry we can't come up with something more solid for you on this one. Like Pat said, using a capacitor to get factory-like gauges will be problematic to engineer. Other folks keep throwing the idea at me, but the best it could offer would be to make it a bit less bouncy.... not a solid gauge like the original. Some people have suggested a circuit board to do the same work via software, but an electonics designer I am definitely not.

Putting the capacitive sender is possible, but it would involve cutting a new mounting hole on the top of the gas tank, and without dropping it down to get a good look at it I can't guarantee that you will have the clearance for it. They seem to be a bit bulkier up top, and I believe that the fuel pump/sender assembly has a recessed section in the tank top to fit it into. A side-mounted sender would probably be more difficult to seal up properly, and leaking gas is something we need to avoid causing.

Swapping the guts between the gauges may be an option.... though I'd probably suggest swapping the factory guts into the Classic Gauge housing, to keep it all matching nicely if possible.

-Hans
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  #17  
Old June 12th, 2006, 12:44 AM
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sorry-that what i was getting at(swapping factory guts into the classic house). i am going to check that out in the a.m.
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  #18  
Old June 13th, 2006, 12:27 AM
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i called this morning and they said they could- and he said some thing to the effect of it could cost $500-$1000 ?@!#% so i called a few gauge shops around the U.S. they all said that guy was smoking crack. everyone else said about $75-$150. so i decided to take the factory gauge apart and it looks like it would be a pretty simple swap. i just dont know how to get the other gauge open with out destroying it? the factory gauge i opened buy cutintg the black ring around it to hold the lense in.

Follow-up Post:

by the way it seems it maybe pulsing also-so tried running a new ground wire, that did nothing
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  #19  
Old June 13th, 2006, 02:17 AM
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That is what is sometimes called the "Go-Away" price. They don't want to do the work, so they will tell you a price that is well above what somebody would willingly pay for it.

-Hans
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