Fuel Gauge issue

[Muscled_up]

I have a 12/2007 night train FXSTB and recently took the original fuel caps/gauge off and replaced with RSD tach caps.

I went with the non LED dummy cap as i have a fuel gauge in dash but since unplugging originl gauge my dash gauge no longer  works and shows fuel light on.

Does anyone know what i can do to fix this?
If i put the LED RSD tech cap will that complete circuit and make gauge work again

Any info would be greatly appreciated

Cheers

[Soft 02]

You need a resistor wired into the plug. That all I remember. I will be doing the same thing down the road. I got the tack/speedo that has a digital fuel gauge in it.

[Muscled_up]

Thanks for that i guess you have similar gauge as im using in pic

Do you know where i can get a resistor or who sells them.
Im also based in OZ so no local electrical store would work for me

Cheers

[Soft 02]

You will probably get more info as people chime in. Im not ready to do mine so I havnt done the research yet. The resistor tricks the fuel light into thinkin you have fuel in the tank.

[FSG]

I believe the Dash Gauge and the Cap Gauge are wired in parallel, I'll take a look.

[Soft 02]

That's the dash I have and you still need the fuel cap gauge for it to work. I think the OP is using the stock speedo and wants to ditch the gauge all together and not have a low fuel light on the dash.

[FSG]

I think the OP wants the Dash Gauge to work and in doing so the low fuel light will go out.

M/Up temporarily reconnect the orig cap gauge to the plug under the tank, what then does the Dash Gauge and Low Light do?

[Soft 02]

Did that on mine an fuel light comes on immediately.

[FSG]

Parallel   

[Soft 02]

So what value resistor will shut the fuel light off if put in parallel replacing the gauge?

[FSG]

there's more to it than meets the eye

[Muscled_up]

I think the OP wants the Dash Gauge to work and in doing so the low fuel light will go out.

M/Up temporarily reconnect the orig cap gauge to the plug under the tank, what then does the Dash Gauge and Low Light do?

Yes FSG that is correct i have a LCD in the base of the speedo and didnt expect it to stop working
i have not tried plugging in the original ill need to do it

[Soft 02]

Mine said no gear indicator but that function works fine. Only thing that doesn't work is the range till empty. I also find the digital fuel indicator seems more accurate than the analog cap one. For this reason I will ditch the factory one someday.

[Soft 02]

I also have considered bagging up the internals of the stock gauge and stuffing it under the tank because I have a tank lift.

[Muscled_up]

I read somewhere someone has done that but it sounds dodgy

Surely they can make a plug that fits the original that fixes the issue

[Soft 02]

I wish.

[FSG]

OK what actual revision of COMBINATION SPEEDOMETER/TACHOMETER GAUGE  do you guys have?

As some functionality has been updated.

[FSG]

Rev A   functionality

[Soft 02]

I don't know. Next time I have the dash off I'll take a pic for future reference. According to the paperwork I had the gear indicator wasn't supposed to work. If there is a way to eliminate the dial fuel gauge many would be interested. Thanks for the info regardless FSG.

[Muscled_up]

I wouldnt have a clue FSG i just plugged original back in and light goes out and LCD dash fuel guage works but unlug and it goes out again

[Muscled_up]

Is it possible to change the backlight colour on these speedo i got mine on bike and have no instructions with it?

[Soft 02]

Yes but I'll have to find my box. Think its out in my shop. 600 color options. Pretty cool.

[FSG]

http://www.harley-davidson.com/en_US/Media/downloads/Service/isheets/-J05306.pdf

[Muscled_up]

http://www.harley-davidson.com/en_US/Media/downloads/Service/isheets/-J05306.pdf

Thanks FSG awesome info

[FSG]

OK, the LCD dash fuel gauge is NOT going to work without the Tank Gauge or without it being fooled to think the tank gauge is still there because without the gauge there is no voltage divider to create the signal to the Speedo.

OK take a good Multimeter on Ohms x 1 (by 1) and measure the resistance between pins 1 and 2 of the actual tank fuel gauge. 

This is the value of resistor that will be required to install across pins 1 and 2 of the empty socket 117B after the removal of the tank gauge.

[FSG]

So does anyone have a spare stock softail fuel gauge and can measure and post the DC Resistance of the gauge?

[UltraNutZ]

Brian, the problem is not so much the voltage or the resistance of the sending unit, the resistance of the gauge itself, or the voltage divider and the only constant in this equation is the voltage divider.  The issues are the varying voltages and varying resistances as fuel levels increase and decrease in the tank.  I've tried this numerous times throughout the past couple of years for guys that wanted to eliminate the stocker fuel gauges in fairings as well as tank mounted to no happy end result.  It either would show

   
• fuel gauge would show full tank with a full tank but the fuel light would come on within 50 or so miles sometimes less sometimes more
• fuel gauge would show only partial tank (usually between 1/4 to 3/4) with a full tank of fuel and fuel light was on at 1/2 tank
• fuel light would come on and stay on regardless of amount of fuel.

The end-result was either plugging the stock gauge back in and zip tying it out the way in fairing bikes or pulling apart the fuel cap, removing the circuit board, insulating it, and stuffing it back down the hole with their cute decorative trim cover on it.

Not saying it can't be done and knowing you, you'll take this as a challenge to get it done..     Just spent a lot of time chasing it to no resolve.


to answer your question though, if no one ponies up the resistance, I'll get it for you when I get home

[Muscled_up]

Brian, the problem is not so much the voltage or the resistance of the sending unit, the resistance of the gauge itself, or the voltage divider and the only constant in this equation is the voltage divider.  The issues are the varying voltages and varying resistances as fuel levels increase and decrease in the tank.  I've tried this numerous times throughout the past couple of years for guys that wanted to eliminate the stocker fuel gauges in fairings as well as tank mounted to no happy end result.  It either would show

   
• fuel gauge would show full tank with a full tank but the fuel light would come on within 50 or so miles sometimes less sometimes more
• fuel gauge would show only partial tank (usually between 1/4 to 3/4) with a full tank of fuel and fuel light was on at 1/2 tank
• fuel light would come on and stay on regardless of amount of fuel.

The end-result was either plugging the stock gauge back in and zip tying it out the way in fairing bikes or pulling apart the fuel cap, removing the circuit board, insulating it, and stuffing it back down the hole with their cute decorative trim cover on it.

Not saying it can't be done and knowing you, you'll take this as a challenge to get it done..     Just spent a lot of time chasing it to no resolve.


to answer your question though, if no one ponies up the resistance, I'll get it for you when I get home

I have found online it varies as the fuel decreases.
Are you saying your able to pull the guage apart and just leave it sitting idle as a circuit board in the void in the tank.
Can you tell me how far i need to strip the original guage to allow it to work but be small enough to allow my RSD dummy cap to fit.

[FSG]

I have found online it varies as the fuel decreases.

What is the IT you are referring to there?

The DC resistance of the fuel gauge cannot change.

The DC resistance of the fuel tank sender will change, that's it's purpose, so the current flowing through the fuel gauge will change and in doing so will move the needle from full to empty.  Also at the same time the voltage on the speedo pin 9 will change from a low value to a high value, thus driving the LCD Display input.

[UltraNutZ]

Brian, the problem is not so much the voltage or the resistance of the sending unit, the resistance of the gauge itself, or the voltage divider and the only constant in this equation is the voltage divider.  The issues are the varying voltages and varying resistances as fuel levels increase and decrease in the tank.  I've tried this numerous times throughout the past couple of years for guys that wanted to eliminate the stocker fuel gauges in fairings as well as tank mounted to no happy end result.  It either would show

   
• fuel gauge would show full tank with a full tank but the fuel light would come on within 50 or so miles sometimes less sometimes more
• fuel gauge would show only partial tank (usually between 1/4 to 3/4) with a full tank of fuel and fuel light was on at 1/2 tank
• fuel light would come on and stay on regardless of amount of fuel.

The end-result was either plugging the stock gauge back in and zip tying it out the way in fairing bikes or pulling apart the fuel cap, removing the circuit board, insulating it, and stuffing it back down the hole with their cute decorative trim cover on it.

Not saying it can't be done and knowing you, you'll take this as a challenge to get it done..     Just spent a lot of time chasing it to no resolve.


to answer your question though, if no one ponies up the resistance, I'll get it for you when I get home

Are you saying your able to pull the guage apart and just leave it sitting idle as a circuit board in the void in the tank.

yes sir that's what's I'm saying.  Pull the gauge apart, all you need is the circuit board.  Plug it back in, wrap it in electrical tape or heat shrink and stick it back down in the bottom of the gauge hole.  Put your fancy cover over it.

[UltraNutZ]

I have found online it varies as the fuel decreases.

What is the IT you are referring to there?

The DC resistance of the fuel gauge cannot change.

The DC resistance of the fuel tank sender will change, that's it's purpose, so the current flowing through the fuel gauge will change and in doing so will move the needle from full to empty.  Also at the same time the voltage on the speedo pin 9 will change from a low value to a high value, thus driving the LCD Display input.

you are correct.  The fuel gauge IS the voltage divider in this circuit.  Unless I'm completely missing something, using a voltage divider previously provided no accurate or useful results in my tests. 

Sorry bud I got wrapped up in changing cams on that softail yesterday afternoon so forgot to measure the fuel gauge for you.  I'll do it this afternoon when I get home.

[Muscled_up]

Brian, the problem is not so much the voltage or the resistance of the sending unit, the resistance of the gauge itself, or the voltage divider and the only constant in this equation is the voltage divider.  The issues are the varying voltages and varying resistances as fuel levels increase and decrease in the tank.  I've tried this numerous times throughout the past couple of years for guys that wanted to eliminate the stocker fuel gauges in fairings as well as tank mounted to no happy end result.  It either would show

   
• fuel gauge would show full tank with a full tank but the fuel light would come on within 50 or so miles sometimes less sometimes more
• fuel gauge would show only partial tank (usually between 1/4 to 3/4) with a full tank of fuel and fuel light was on at 1/2 tank
• fuel light would come on and stay on regardless of amount of fuel.

The end-result was either plugging the stock gauge back in and zip tying it out the way in fairing bikes or pulling apart the fuel cap, removing the circuit board, insulating it, and stuffing it back down the hole with their cute decorative trim cover on it.


yes sir that's what's I'm saying.  Pull the gauge apart, all you need is the circuit board.  Plug it back in, wrap it in electrical tape or heat shrink and stick it back down in the bottom of the gauge hole.  Put your fancy cover over it.

I did this this morning and it worked but then went back to not working
I attached the face and needle set up and it worked but after a bit stopped working so im not sure anymore whether this will work or i have done something wrong.
I have not wrapped it yet so not sure if circuit board is touching metal, i placed in a plastic bag but it stopped even after doing that.

Im going for a ride tomorrow so i will see what it does on the ride

[UltraNutZ]

I have found online it varies as the fuel decreases.

What is the IT you are referring to there?

The DC resistance of the fuel gauge cannot change.

The DC resistance of the fuel tank sender will change, that's it's purpose, so the current flowing through the fuel gauge will change and in doing so will move the needle from full to empty.  Also at the same time the voltage on the speedo pin 9 will change from a low value to a high value, thus driving the LCD Display input.

Where do you need resistance measured on the stock fuel gauge?

[UltraNutZ]

I did this this morning and it worked but then went back to not working
I attached the face and needle set up and it worked but after a bit stopped working so im not sure anymore whether this will work or i have done something wrong.
I have not wrapped it yet so not sure if circuit board is touching metal, i placed in a plastic bag but it stopped even after doing that.

Im going for a ride tomorrow so i will see what it does on the ride

I've done this same thing at least 5 or 6 times over the past couple of years without issue both with tank mounted fuel gauges and fairing mounted gauges.

[FSG]

Where do you need resistance measured on the stock fuel gauge?

Between Pins 1 and 2, thanks.

[UltraNutZ]

4.36m Ω

[Karl H.]

Isn't this item available in US?



Dealer: www.zodiac.nl

[UltraNutZ]

I saw that some time ago but in my searches, apparently not.  Wonder what's neatly tucked into that heat-shrink.

[UltraNutZ]

take that back.. appears that it is available.

http://www.granitestateharleystore.com/Performance%20Machine%20Inc.-LOW%20FUEL%20LIGHT%20ELIMINATOR%20PLUG-detail.htm?productId=18393813

http://www.amazon.com/Performance-Machine-Light-Eliminator-0210-2026/dp/B00DTEBI4Q

[Karl H.]

 

[FSG]

Wonder what's neatly tucked into that heat-shrink.

Probably something close to a 4.36M Ohm Resistor, which can be had for cents from Radio Shack / Jaycar.

[UltraNutZ]

I'll tell you for sure on Dec 1 when it arrives.  I ordered a couple of them.  This pinky bike I had here wants to do the same thing.

[Muscled_up]

I pulled gauge apart and have sat it back in void in tank but it is still not working

I tried just circuit board then with fuel needle assembly but it wasn't working so ill look at getting one of these plug in fixer lol

Cheers

[FSG]

I'm going to be cautious with regard to these "LOW FUEL LIGHT ELIMINATOR PLUG"s as they are designed to

A: turn off the low fuel warning light in the speedometer
B: For use when removing factory fuel gauge

of course this could be achieved using a resistor value such that regardless of the actual fuel level and float position the voltage divider would always read at or near to a full tank. 

Yes the warning light in the speedo would never come on but at the same time the LCD Fuel Level Display would be next to useless.

A question for Performance Machine / Zodiac would be "will these eliminators still enable the LCD Fuel Level in the Speedo to still operate"?


M/Up can you post pix of your disassembled gauge?

[Muscled_up]

I'm going to be cautious with regard to these "LOW FUEL LIGHT ELIMINATOR PLUG"s as they are designed to

A: turn off the low fuel warning light in the speedometer
B: For use when removing factory fuel gauge

of course this could be achieved using a resistor value such that regardless of the actual fuel level and float position the voltage divider would always read at or near to a full tank. 

Yes the warning light in the speedo would never come on but at the same time the LCD Fuel Level Display would be next to useless.

A question for Performance Machine / Zodiac would be "will these eliminators still enable the LCD Fuel Level in the Speedo to still operate"?


M/Up can you post pix of your disassembled gauge?

Ill take some pics for you FSG
I thought the same thing whether guage will work or just stop the fuel light coming on.
Im hoping it works as it wasnt cheap as they A## R#ped me on postage
I know you say the resistors are cheap FSG but im basic and dont have the understandings you have of the electrics and the workings of it all.
I appreciate all the input everyone has shared here

[Muscled_up]

Pics

[FSG]

Tks, I'd like to get my hands on that and put it under the microscope, I'll bet they have Surface Mount Resistors across the input.

Do you have a Jaycar Outlet anywhere near you?

[UltraNutZ]

muscled_up.. what exactly "isn't working".  Does the low fuel indicator stay on, does your fuel gauge read incorrectly?

Taking the fuel gauge out of the housing, wrapping it up in electrical tape or putting it in a baggie and sticking it back down the hole ain't no different than having the fuel gauge mounted on top of the tank.  Doesn't make any sense.

By chance have you re-calibrated your fuel gauge again on the dash with the instructions provided with the speedo since you started fooling with this?

[UltraNutZ]

I'm going to be cautious with regard to these "LOW FUEL LIGHT ELIMINATOR PLUG"s as they are designed to

A: turn off the low fuel warning light in the speedometer
B: For use when removing factory fuel gauge

of course this could be achieved using a resistor value such that regardless of the actual fuel level and float position the voltage divider would always read at or near to a full tank. 

Yes the warning light in the speedo would never come on but at the same time the LCD Fuel Level Display would be next to useless.

A question for Performance Machine / Zodiac would be "will these eliminators still enable the LCD Fuel Level in the Speedo to still operate"?


M/Up can you post pix of your disassembled gauge?

And yes FSG you are absolutely correct.  All this does is inject a resistor inline to keep the low fuel light from illuminating.  The guys are PM couldn't (or wouldn't) tell me anything else about the device but it's obviously a fixed value set at something above the "low fuel" resistance value.  I'll tear it apart when it gets here.

muscled_up, afraid this won't do anything for you other than turn your low fuel light off.  won't do anything for your fuel gauge not working.

[Soft 02]

Still it would let you ditch the factory gauge. Wonder if it messes with the LCD gauge.

[FSG]

M/Up where in Brisbane are you, perhaps I can visit and get a better look at that gauge.

[UltraNutZ]

Those speedo combo things are designed to be used with stock gauge in tact.  Still think he should try to recalibrate the gauge per the HD instructions that came with it

[Karl H.]

I found two wiring graphs from HD literature explaining the function of the fuel gauge and sending unit.
Replacing the gauge coil by a resistor should maintain the functionality of the low fuel light as well as of a speedo integrated LCD gauge.



Karl

[FSG]

Ultra was that 4.3M in both directions?

Can you also measure between pins 2 and 3 in both directions?

[Muscled_up]

M/Up where in Brisbane are you, perhaps I can visit and get a better look at that gauge.

I live in Redland Bay FSG and i could come to you so your not put out if you want to pull it apart and work it out

What part are you in?

If you are keen let me know and i could PM you a mobile number to call

[Muscled_up]

muscled_up.. what exactly "isn't working".  Does the low fuel indicator stay on, does your fuel gauge read incorrectly?

Taking the fuel gauge out of the housing, wrapping it up in electrical tape or putting it in a baggie and sticking it back down the hole ain't no different than having the fuel gauge mounted on top of the tank.  Doesn't make any sense.

By chance have you re-calibrated your fuel gauge again on the dash with the instructions provided with the speedo since you started fooling with this?

The gauge will read empty with warning on then read full on LED gauge.

No i havent recalibrated as i dont know how or have any instructions as it was on bike when i got it.
Also 1st to 5th gear indicators dont work anymore and 6th gear does work

Hopefully i can catch up with FSG in person and he can steer me in right direction

[UltraNutZ]

here's the link for programming and calibration instructions.  Take a look at page 4, Fuel Level Display

http://www.harley-davidson.com/app-content/service/isheets/-J05306.PDF

[FSG]

M/Up came over earlier today and left an hour or so ago.

There's more to it than meets the eye, there always is.      With his HD Fuel Gauge dismantled we could dismantle it some more removing the meter movement from the PCB, measuring with the trusty Simpson 260.  Well the full schematic has been drawn out and a voltage divider made which has been soldered in across the Orange, Yellow and Black wires.  M/Up will confirm operation of the Speedo LCD Fuel Display as the fuel is consumed during the use of the bike over the next few days.

Once confirmed I'll put a full schematic up on HTT. 

[FSG]

Some pix.  The meter movement is mechanically well damped.

http://imageshack.com/i/paFnyyeQp



Note the two Clear LEDS (Amber when lit) and the Current Limiting Resistor which provide the internal lighting.  The Diode protects the meter in case of reversed polarity power.

http://imageshack.com/i/p1AtmeKep



Solder side.

http://imageshack.com/i/p9pcnLc2p



There are another two resistors, one of which is across one of the meters coils, these resistors form an internal voltage divider.  Yes the resistor leads have been cut, removes them from circuit so as to get accurate measurements of the meter coils resistance.

http://imageshack.com/i/iptUbUpLp


Removing the meter from the board and just stuffing the board into the tank hole and cover on top is not going to work.

[Karl H.]

Good info! 
Look forward to seeing the schematic! 

[FSG]

With my bench test setup I can sweep this Fuel Gauge from Empty to Full

http://tinypic.com/r/29opezo/8

and from Full to Empty, so I'm confident I've a good handle on its operation and that the Voltage Divider now in M/Ups Ride will provide the required result.

http://tinypic.com/r/2dj6ofk/8

[Soft 02]

Very good work! If this works I will be doing the same. Thanks op an FSG.

[UltraNutZ]

and I thought I was the tinkerer.  Nice work!  Let us know the results.

[UltraNutZ]

ok so to follow this up..

got the device in today.




cut her open



and this is what I found..  330Ω 1%

[Karl H.]

330 Ohm makes definitly more sense than 4.36 mOhm. 

Karl

[UltraNutZ]

well keep in mind my original measurements were with all the crap that FSG pointed out above as being inside the fuel gauge housing.

[Karl H.]

The 330 Ohm should equal the resistance of the gauge unit including the resistors FSG found.

I put a voltage divider into the original HD schematic which should make the unit work.
The equation R1+R2=330 Ohm should be correct imho.

[FSG]

The R1 &  R2 in Karls pic are 220 ohms each,  what that pic doesn't show is the other meter coil going to ground.  A single resistor will stop the low fuel light from coming on which is all this device from PM and others is wanting to do,  but to have the fuel LCD display on the speed operate correctly two resistors forming a voltage dinner replacing the gauge are required.

Waiting on M/Up to post results of his gauge operation as his bike burns fuel.

[Karl H.]

Thanks FSG for the clarification. If there are two coils it's a "Balance Coil Gauge" most likely



Speedy Jim explains how it works: http://www.speedyjim.net/htm/fuel_ga.htm (scroll down!)

Karl

[FSG]

K,  you have it in one.  Dual coil,  I would post the schematic but prefer to see M Up post first.

[jty]

Found this old thread, is it possible to get the fuel gauge schematics available?

[Karl H.]

That's what I could measure:

[attach=0,msg1313811]

[Rusticwater]

Karl is the R2 value a misprint, referring to FSG's post #67? 

[Karl H.]

Karl is the R2 value a misprint, referring to FSG's post #67? 

No it isn't! I couldn't believe it and measured several times. The corresponding signature shows "0R0". The values in post #67 are from elsewhere but not my own findings.

[attach=0,msg1313816]

Karl

[Rusticwater]

Thank you for the clarification.