Home » Public Forums » GMCnet » Fuel Gauge Sender Ohms (Don't Know Resistors from Nuttin')
| Fuel Gauge Sender Ohms [message #282241] |
Thu, 16 July 2015 14:08  |
George Beckman
Messages: 1085
Registered: October 2008
Location: Colfax, CA
Karma: 11
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Senior Member |
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I am eyeing new gauges. The gauges I currently am leaning toward are Autometer and the fuel is 240 ohms empty to 33 ohms full. I am thinking that there is no way to "simply" change our 0-90 to this new range because it is upside down and a different range.
I guess what I am hoping for is to be able to reverse the polarity of the wires and put a resistor-gizmo in the line and get this to work- sorta. After all I am not overly impressed with the original setup. Mine is waaaaay full when it is full, stays there for 7-8 gallons, moves slowly to 3/4 and falls off like a hole was torn in the tank.
I know, it all has to do with the tanks swapping until the level is down and then really using from just one tank. I am sure my TBI return adds to the confusion here.
So, you folks that know about farads, ohms and linear stuff, can this be done or do I need to get a stick to poke down in the tank?
'74 Eleganza, SE, Howell + EBL
Best Wishes,
George
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| Re: [GMCnet] Fuel Gauge Sender Ohms [message #282242 is a reply to message #282241] |
Thu, 16 July 2015 14:33  |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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Stick is a heck of a lot more accurate, George. Hard to use, though. I
kind of ignore my fuel gages, and go by miles traveled. System holds 50
gallons. Get about 10 mpg. I average 50 mph while traveling so every 4
hours of driving, I stop and refuel both me and the coach. I personally
never drive on the bottom half of the tank in any vehicle I have. Other
people seem to enjoy sweating bullets over the last bit of fuel in their
gmc and instead rely upon AAA to manage their fuel reserve. The last time I
ran out of fuel was when I was 17 or 18 driving my mom's 1947 Plymouth
sedan that had an optimistic sending unit. On the freeway late at night
with dates in the car. Ruined my whole plans for the evening. Vowed to
never let that happen again. Hasn't so far, and I'm 75.
Jim Hupy
Salem, Or
78 GMC ROYALE 403
On Jul 16, 2015 12:09 PM, "George Beckman" wrote:
> I am eyeing new gauges. The gauges I currently am leaning toward are
> Autometer and the fuel is 240 ohms empty to 33 ohms full. I am thinking that
> there is no way to "simply" change our 0-90 to this new range because it
> is upside down and a different range.
>
> I guess what I am hoping for is to be able to reverse the polarity of the
> wires and put a resistor-gizmo in the line and get this to work- sorta.
> After all I am not overly impressed with the original setup. Mine is
> waaaaay full when it is full, stays there for 7-8 gallons, moves slowly to
> 3/4
> and falls off like a hole was torn in the tank.
>
> I know, it all has to do with the tanks swapping until the level is down
> and then really using from just one tank. I am sure my TBI return adds to
> the
> confusion here.
>
> So, you folks that know about farads, ohms and linear stuff, can this be
> done or do I need to get a stick to poke down in the tank?
>
> --
> '74 Eleganza, SE, Howell + EBL
> Best Wishes,
> George
>
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| Re: Fuel Gauge Sender Ohms [message #282244 is a reply to message #282241] |
Thu, 16 July 2015 15:04 |
A Hamilto
Messages: 4508
Registered: April 2011
Karma: 39
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Senior Member |
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George Beckman wrote on Thu, 16 July 2015 14:08I am eyeing new gauges. The gauges I currently am leaning toward are Autometer and the fuel is 240 ohms empty to 33 ohms full. I am thinking that there is no way to "simply" change our 0-90 to this new range because it is upside down and a different range.
I guess what I am hoping for is to be able to reverse the polarity of the wires and put a resistor-gizmo in the line and get this to work- sorta. After all I am not overly impressed with the original setup. Mine is waaaaay full when it is full, stays there for 7-8 gallons, moves slowly to 3/4 and falls off like a hole was torn in the tank.
I know, it all has to do with the tanks swapping until the level is down and then really using from just one tank. I am sure my TBI return adds to the confusion here.
So, you folks that know about farads, ohms and linear stuff, can this be done or do I need to get a stick to poke down in the tank? Not gonna reverse the polarity by reversing the wires. you would have to flip the float arrangement in the tank. You are going to need something like an op-amp circuit to amplify and reverse the slope of the variable resistance of the float. You want a 0 - 90 ohm resistance to linearly range from 240 to 33. In other words, when the resistance of the float resistor is 90, you want 33 ohms, and when the float resistor is 0 you want 240 ohms with everything in between forming a straight line on a chart. I'll see if I can find something on the web, since college was decades ago and my career was more project management than tinkering.
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| Re: Fuel Gauge Sender Ohms [message #282248 is a reply to message #282245] |
Thu, 16 July 2015 15:57 |
A Hamilto
Messages: 4508
Registered: April 2011
Karma: 39
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Senior Member |
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After reading subsequent posts and giving it some thought, your problem is probably with the behavior of the float in the tank, not the gauge. If you want accurate readings at the gauge, you would need to start with a float/sender in the tank that is well behaved. Your gauge is probably as good as it is going to get with the floats/senders you have.
It is possible to design an electronic gizmo that will convert to accurate readings. You would need to start with an empty tank and then add a gallon, shake the tank a little to get the float where it wants to be, record the resistance of the sender, add a gallon, shake the tank, read the resistance of the sender, repeat until the tank is full. Then build a circuit that will convert the readings to linear, or at least make full = full and 1/4 = 1/4.
Question for the GMC brain trust: Is the fuel gauge a voltmeter or an ammeter?
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| Re: Fuel Gauge Sender Ohms [message #282249 is a reply to message #282248] |
Thu, 16 July 2015 16:23 |
bpimm
Messages: 211
Registered: June 2013
Location: Washougal Washington
Karma: 2
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Senior Member |
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Neither its a fuel meter... Sorry I had to. I'm going to say it's an amp meter, assuming that the gauge is hooked from the sender to +, which my schematic doesn't show, the changing resistance of the sender would change the current flowing through the gauge. If it were a volt meter I would expect to see the sender between + and ground and the wiper going to the gauge.
Brian & RaeDean
1973 26' #383
Washougal WA
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| Re: [GMCnet] Fuel Gauge Sender Ohms [message #282250 is a reply to message #282248] |
Thu, 16 July 2015 16:22 |
k2gkk
Messages: 4452
Registered: November 2009
Karma: -8
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Senior Member |
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I'd say that all D'Arsonval meters are actually ammeters; that is, they respond to the amount of current in the moving coil. Some dials arfe calibrated in equivalent voltages or other quantities (tank capacity, for example).
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
~~ ~ D C "Mac" Macdonald ~ ~~
~ ~ Amateur Radio - K2GKK ~ ~
~ ~ Since 30 November '53 ~ ~
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~ Member GMCMI and Classics ~
~ ~ ~ Oklahoma City, OK ~ ~ ~
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"--OO--[]---O-"
> Date: Thu, 16 Jul 2015 14:57:37 -0600
> To: gmclist@list.gmcnet.org
> From: markbb1@netzero.com
> Subject: Re: [GMCnet] Fuel Gauge Sender Ohms
>
> After reading subsequent posts and giving it some thought, your problem is probably with the behavior of the float in the tank, not the gauge. If you
> want accurate readings at the gauge, you would need to start with a float/sender in the tank that is well behaved. Your gauge is probably as good as
> it is going to get with the floats/senders you have.
>
> It is possible to design an electronic gizmo that will convert to accurate readings. You would need to start with an empty tank and then add a
> gallon, shake the tank a little to get the float where it wants to be, record the resistance of the sender, add a gallon, shake the tank, read the
> resistance of the sender, repeat until the tank is full. Then build a circuit that will convert the readings to linear, or at least make full = full
> and 1/4 = 1/4.
>
> Question for the GMC brain trust: Is the fuel gauge a voltmeter or an ammeter?
> --
> '73 23' Sequoia For Sale
> '73 23' CanyonLands For Sale
> Upper Alabama
> On "marriage equality": Once you define the direction that society is headed as "forward", you can call it progress.
>
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| Re: [GMCnet] Fuel Gauge Sender Ohms [message #282278 is a reply to message #282250] |
Thu, 16 July 2015 22:53 |
Bullitthead
Messages: 1411
Registered: November 2013
Karma: 5
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Senior Member |
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"I'd say that all D'Arsonval meters are actually ammeters; that is, they respond to the amount of current in the moving coil. Some dials arfe calibrated in equivalent voltages or other quantities (tank capacity, for example)."
You would say that and you would be correct, Mac.
Terry Kelpien
ASE Master Technician
73 Glacier 260
Smithfield, Va.
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| Re: [GMCnet] Fuel Gauge Sender Ohms [message #282281 is a reply to message #282278] |
Thu, 16 July 2015 23:02 |
k2gkk
Messages: 4452
Registered: November 2009
Karma: -8
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Senior Member |
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I've been doin' this stuff as amateur and then military and commercial for almost 62 years, Terry!
I've not done the high power stuff that Johnny Bridges has done and still does, but the basics remain the same.
I'm not much of a mechanic, though. Last "heavy" stuff was rebuilding a 1950 Ford flathead V-8 back in 1958 after I blew the side out of piston at the Wattsburg, PA dragstrip.
Cheers - Mac
> Date: Thu, 16 Jul 2015 21:53:38 -0600
> To: gmclist@list.gmcnet.org
> From: mrbullitt@verizon.net
> Subject: Re: [GMCnet] Fuel Gauge Sender Ohms
>
> "I'd say that all D'Arsonval meters are actually ammeters; that is, they respond to the amount of current in the moving coil. Some dials arfe
> calibrated in equivalent voltages or other quantities (tank capacity, for example)."
>
> You would say that and you would be correct, Mac.
> --
> Terry Kelpien
> ASE Master Technician
> 73 Glacier 260
> Smithfield, Va.
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| Re: Fuel Gauge Sender Ohms [message #282301 is a reply to message #282241] |
Fri, 17 July 2015 08:04 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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George -
I'd call Autometer and see what they offer in a 90 ohm cluster. Surely you aren't the only person who ever wanted to fit one to a 70s GM product. I can think of a couple ways one might interface 230 to 90, but it would be a total PIA and increase both the parts count and connection count (and consequently the failure modes) substantially. Kinda like the microprocessor controlled flashlight. I bought a set of cheeeep digital gauges from the Heathen Chinee, I haven't decided do I put them in the coach or in the rat rod toad pickup. Likely gona be the pickup, I'm not getting any nibbles to sell it, I may just keep it.
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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