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Low Fuel Indicator Light Blinking

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Someassemblyrqd View Drop Down
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    Posted: Dec/03/2018 at 7:09pm
just replaced by failed fuel level sending unit. Calibrated and verified the unit and confirmed the gauge has full sweep empty to full.   However, it appears no good deed goes unpunished.

The low fuel indicator dimmly blinks when the gauge is between 1/4 and full.   The indicator light blinks brightly at a 1/4 tank and below ( I thought the low fuel light was come on and stay on at/below 1/4 tank).   Basically, it’s blinking all the time.

Can I get your thoughts, ideas to resolve this situation.   I do have another low fuel indicator as backup, but it’s something else, I’d like to know.

I anxiously await your responses.  Greg
Greg E.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 304-dude Quote  Post ReplyReply Direct Link To This Post Posted: Dec/03/2018 at 7:19pm
Was the low fuel warning properly functioning before the fuel sender replacement, or was it installed some time go before the tank was dropped for change out?

I think it is possible that the warning unit may have been installed without the isolator. It is needed to isolate the voltage given by the cluster to not over drive the warning module's own internal voltage. It is possible that the internal voltage regulator of the device went bad, and is not supplying a proper voltage for function, if the module has had a long life of function.
71 Javelin SST body
390 69 crank, 70 block & heads
NASCAR SB2 rods & pistons
78 Jeep TH400 w/ 2.76 Low
50/50 Ford-AMC Suspension
79 F150 rear & 8.8 axles
Ford Racing 3.25 gears & 9" /w Detroit locker
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Someassemblyrqd Quote  Post ReplyReply Direct Link To This Post Posted: Dec/03/2018 at 10:11pm
James - what is the isolator, where does it go, and it’s function?  I reinstalled the low fuel gauge into the instrument cluster during my rebuild.  I didn’t think I missed any steps, but then again.......

As I said, I do have an additional low fuel module I purchased from another Forum member after I couldn’t locate my original unit.   I don’t want to take a chance of damaging this additional unit without understanding what issues may be causing my problem.

Thanks for the additional info
Greg E.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 304-dude Quote  Post ReplyReply Direct Link To This Post Posted: Dec/04/2018 at 4:36am
Note... read all the text before using the image for reference. The plug to the gauge is in the wrong location for clarity of the isolation washer. I doing so i created a bit of confusion.

OK,  I assume you misplaced the opaque  plastic washer that is to be mounted under the speed nut to the fuel gauge.

If you do not have one available, modifying a plastic bottle cap will work.  Just drill a hole of the same diameter as the gauge's stud and trim to a wee larger diameter of the circuit trace's pad,  so no voltage will pass onto the stud when mounted. 

Below I my edited image to show locations for hook up. Note, the connector over the fuel gauge stud is NOT in its proper location. If you zoom in on the fuel gauge stud you will see the opaque washer below the speed nut. I guess when I moved the plug to  allow a clear picture of the washer, I forgot to mention why the connection is wrong.

So, as of now, I labeled to explain that it must be moved over to the isolated stud. 

 At the time of my post, I must have been thinking I would explain, but left it as is, to confuse myself and every one else. 




Edited by 304-dude - Dec/04/2018 at 5:21am
71 Javelin SST body
390 69 crank, 70 block & heads
NASCAR SB2 rods & pistons
78 Jeep TH400 w/ 2.76 Low
50/50 Ford-AMC Suspension
79 F150 rear & 8.8 axles
Ford Racing 3.25 gears & 9" /w Detroit locker
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Someassemblyrqd Quote  Post ReplyReply Direct Link To This Post Posted: Dec/04/2018 at 11:50am
I have a ‘70 AMX, I’ll se if I can adapt the photo diagram and explanation to my instrument panel.

So, the isolator washer needs to go under the speed nut? -  I didn’t have the washer and is not located under the nut.  It’s the little things, I guess.

Thanks
Greg E.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 304-dude Quote  Post ReplyReply Direct Link To This Post Posted: Dec/04/2018 at 12:10pm
ah, i can post the link for earlier Javelin and Hornet.

On the link below, fuzzface2 has an image, look down at the IVR both connections are left and right of it. You can see the washer under the speed nut.



Edited by 304-dude - Dec/04/2018 at 12:17pm
71 Javelin SST body
390 69 crank, 70 block & heads
NASCAR SB2 rods & pistons
78 Jeep TH400 w/ 2.76 Low
50/50 Ford-AMC Suspension
79 F150 rear & 8.8 axles
Ford Racing 3.25 gears & 9" /w Detroit locker
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Someassemblyrqd View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Someassemblyrqd Quote  Post ReplyReply Direct Link To This Post Posted: Dec/04/2018 at 4:07pm
James, Rod - the issue was nothing more than what a hammer couldn’t fit .  Literally!

Age and sitting idle for so long caused the internals of the module to come sticky. I tapped with the end of a Phillips, the dim light went out, and came back on at 1/4 tank.  No blinking. 

Fuel tank going back, go fill up with fuel and move onto the next pickup item before paint at end of month. 

Thanks for all your wisdom. Greg


Edited by Someassemblyrqd - Dec/04/2018 at 8:19pm
Greg E.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote FuzzFace2 Quote  Post ReplyReply Direct Link To This Post Posted: Dec/09/2018 at 9:24am
Good to hear you got it working.
I was not happy with the way mine was working.
IIRC the light came on at half tank when going to empty and go off at 1/4 tank when going to full.
I cant remember if it ever got to full or not?
 
I ended up installing custom Speed Hut Gauges that look stock. They have set points for high / low warning lights.
Sorry to say my project has been put on hold way to long. As soon as I get my other project on the road I will get back on it.
Dave ----
TSM = Technical Service Manual

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70 Javelin 360/T5 Street car
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Someassemblyrqd Quote  Post ReplyReply Direct Link To This Post Posted: Dec/09/2018 at 4:45pm
David - I like the clarity of your gauges, easy to read.  The right side gauge with temp and fuel reminds me of the early 70’s Trans AM gauge clusters.  Greg
Greg E.
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