Replacement "Fuel" Gague

Drive motor and electrical issues

Replacement "Fuel" Gague

Postby jtcweb » Tue Jun 17, 2014 3:30 pm

What is everyone using as a replacement "fuel" gauge. Mine is just barely in the green when I know the bank is fully charged.
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Re: Replacement "Fuel" Gague

Postby Jeff Antonucci » Tue Jun 17, 2014 9:58 pm

This is very common. The resistance of the built in resistor changes (get larger) over time. You can have a new resistor soldered in if you find someone with enough patience to deal with the crazy thin wiring inside. You can also get decals to replace the painted gauge face. I still have some left that I had made up a few years ago.
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Re: Replacement "Fuel" Gague

Postby FarmallMan » Tue Jun 17, 2014 10:45 pm

Jeff's right they read low as the resistance increases over time. They all seem to do this regardless of whether they are NOS or not. I have done the repair in the past, and it can be VERY difficult - what ever you do, don't attempt to cut out the old resistor. You will rue the day you did. If you search for 36 volt state of charge meters, they are still made in round and square formats. The square truly are square, not rounded like ours are, but work the same. I know various vendors carry them. Here's what I'm talking about: http://www.diygolfcart.com/State-Of-Cha ... -p/393.htm

Nick 8-)
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Re: Replacement "Fuel" Gague

Postby jtcweb » Wed Jun 18, 2014 12:43 pm

Well this is a case where my previous work experience will really come in handy. I used to replace chips on computer motherboards back before they became throw-aways. De-soldering a 40-pin DIP Chip takes some patience. Can someone tell me what the value of the resistor should be in case the color bands are no longer visiable?
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Re: Replacement "Fuel" Gague

Postby Jeff Antonucci » Wed Jun 18, 2014 1:07 pm

Nick - was it 5K? It's been a while.
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Re: Replacement "Fuel" Gague

Postby FarmallMan » Wed Jun 18, 2014 1:46 pm

I'll have to open one up and look, since I can't remember either. What I'd advise that you do is check the existing resistance with a multimeter and use the parallel resistance equation to calculate the resistance you would need to add in parallel with the existing resistor to get back to the original value. This approach is a lot simpler and less anxiety producing - TRUST ME. I routinely do surface mount components under a scope with tweezers and an iron.

I'll look probably tonight, or tomorrow at the latest.

Nick 8-)
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Re: Replacement "Fuel" Gague

Postby JohnM » Tue Oct 07, 2014 7:00 pm

VoltMeter.jpeg
VoltMeter.jpeg (342.13 KiB) Viewed 1919 times

Cheap digital volt meter from Adafruit. I tend to think in terms of a 12 volt battery so I chose the two wire 3.2 - 30 VDC version and wired it to read 1/3 of the pack when the disconnect switch is closed. A three wire 0 - 99.9 VDC version is also available. $8 each. Easy to fabricate a mount. The amp meter will be next. The dash of my shortened E15 with the Alltrax install is a work in progress
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Re: Replacement "Fuel" Gague

Postby roberttroll » Wed Oct 08, 2014 12:44 am

can i guess that you used a hole saw to cut those circles out? If you can, please post a link to the meter that you used and the underside of the cutout. Looks like a nice and clean setup!
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Re: Replacement "Fuel" Gague

Postby JohnM » Wed Oct 08, 2014 5:34 pm

Go to Adafruit.com and search for "Volt Meter". Good photos and info.

The ~1/8" thick clear plastic and aluminum disks were both cut using a drill press with a 2 1/2 " hole saw (drill bit retracted for the plastic cut). This resulted in disk diameters of ~2 3/8". The hole in the dash is ~2 1/8" in ID. The aluminum disk diameter was trimmed down on a lathe to just fit inside the dash hole. As you can see from the photo, the ET's dash hole is not perfectly round. You could scribe the disk and hand file it for a better fit. The rectangular center opening in the disk was drilled and hand filed to accept the digital meter module. Disk surfaces were protected with painters tape during fabrication.

Center the aluminum disk over the plastic disk in the desired final position and tape them together. Drill two small holes through both disks on opposite sides for the 6-32 1" machine screws. The holes should be ~1 3/4" apart so that nuts on the backside used to fasten the disks together will clear the dash hole ID when installed. No modification to the ET's thicker than 1/8" dash is necessary.

Remove all tape and fasten the disks together with nuts on the aluminum backside. Insert the digital module into the rectangular cutout against the plastic window. Hold it in place from behind with a wire bridge made from insulated #14 copper wire with a loop bent on each end to fit around the machine screws. Snug it up with a second set of nuts. I'll probably use a silicon bead around the module next time it's accessible. The original meter bracket which bridges the underside of the dash hole is used to secure the new unit in place. The machine screw spacing is a little closer so elongate a hole or drill a new one. The new meter assembly can then be installed just like the original with a third set of nuts.

After the dash is painted I'll silicon seal the exposed plastic edge and under the screw heads for waterproofing. I like the look of the round meters and flush fit, but this installation could be simplified using rectangular shapes. I hope this helps.
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Re: Replacement "Fuel" Gague

Postby jtcweb » Mon Oct 13, 2014 12:09 am

What voltage would be considered "Red" for the fuel gauge. I'm considering trying the digital one.
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