Fuel Gauge range (Ohms)

[SHOkid13]

Doing some research for a replacement dash cluster like the SHOcus has, and I need to know what the range is for the stock fuel level sending unit.

Anyone know?

 

[projectSHO89]

22.4 empty, 145 full according to the note in the 95 EVTM.

Steve

 

[Off Road SHO]

Steve's right again. I just checked a few old fuel pumps I have and that is the approximate Ohmage I read.

Tom

 

[SHOkid13]

22.4 empty, 145 full according to the note in the 95 EVTM.

Steve

Thanks for checking that info Steve, and you too Tom! Much appreciated.

Okay, now another question... Would it be possible (easily, without complex circuitry) to make the ATM-4318 work considering that it is close (16/158 empty/full)? Basically, when the thank is full, it would read almost full, and when the tank is empty, it would read close to empty... So, the ohms need to be moved up when full, and moved down when empty.

The other ones available are the ATM-4314, which is 0/90 E/F; and the ATM-4317, which is 0/30 E/F. Would either one of those be easier to configure correctly?

That's beyond my knowledge of electronics...

 

[SHOkid13]

I asked my dad to check this out... and since he is a electronics whiz, he says...

Matt,
You need two other pieces of information:
1) you need to know is what is the resistance of the fuel gauge
2) you need to know the voltage to the circuit

Once you know the resistance of the meter (in Ohms) then we can know
the
total circuit resistance in both the empty and full conditions. For
example,
if the meter is 30 Ohms, then the circuit has 52.4 empty, 175 full.

Once you know the voltage of the circuit (I doubt it is the battery
voltage
as then the fuel gauge would increase and decrease with the battery
voltage;
perhaps they use a regulated supply of 8-10V) then we can calculate the
current
that corresponds to E and F. In the above example, if the voltage were
10V,
then the currents would be 10/52.4 =.19Amps when empty and 10/175
=.057Amps
when full. With this information I am confident that I could design a
relatively simple circuit that would drive the new gauge. Note I will
also
need to know the resistance of the new gauge. If you cannot get all of
this
information, then we can use an ohmeter to measure the resistance of
the meters
and/or the gauge.

Sweet! So, who wants one?

 

[NJSHO]

there is also a solid state modual in the path from the sender to the gauge that prevents the needle from moving wildly when the gas sloshes around. Its called the slosh modual most appropriatly. I am trying to analyze the circuit to see if it has any impact. I also want to do a full aftermarket gauge dash.

 

[NJSHO]

Also, autometer sells replacement senders that work with their gauges. Id rather not have to drop the tank to install anything but it is an option.

 

[NJSHO]

More news, Autometer has a gauge that you can program. It is in their C2 section. It says u can do custom calibration so it will work with any sender that reads anywhere between 0 and 270 ohms.

 

[SHOkid13]

More news, Autometer has a gauge that you can program. It is in their C2 section. It says u can do custom calibration so it will work with any sender that reads anywhere between 0 and 270 ohms.

yikes... it's $80 more... I guess that's it then. Should be about $500 for a complete cluster replacement...

 

[Gadamski]

Don't fret none...

SHOkid-

the sender unit you are referring to, actually both in this thread, are commonly referred to as being "in the 10-180 range". That means 10 ohms is "about empty" and 180 ohms is "about full". These measurements are derived from resistance readings taken when the float arm is at the bottom for empty (Not the bottom of it's range mind yu, but the bottom of th tank, installed) and the full at the top of a full level tank of fuel (not the top of the sender arms swing arc, although if you dimple the tank you will read higher). Usually stock or OEM gauges vary on the order of 10%, which means your empty readings will be close, and full is full anyway. When you leave the gas station do you check the gauge as much as when you are under a half tank? Ever notice how darn high the needle goes? The same thing happens on the lower end, where your buddys Honda/Hyundai/Ford runs out at the empty mark and the next buddys car runs for 50 miles past a negative 1/4 tank. The OEM sender will probably do ya' just fine, in short.
Have fun!

 

[HoustinoJillian]

but maybe another reason for installing aftermarkit gauges is to that they'd you know, work correctly.

 

[Gadamski]

but maybe another reason for installing aftermarkit gauges is to that they'd you know, work correctly.

"Correctly" is relative here. The "new" gauge is not going to have the benefit of a perfectly calibrated sender, one set to the precise ohm reading required to "dead nut" the indicator needle spot on the E as the car runs out of fuel. Simple things like the amount of corrosion inside the fuel tank will vary this reading. The float style sender float itself typically "freewheels" on it's axis, in Fords typically along the length of the ovalized closed cell polymer float. If this "hangs" in an off center orientation then the sender arc will be compromised, sending the reading off from it's intended signal relative to the real fuel level in the tank. Basically it is all just a crap shoot. There are variences (designed "looseness" to the precision of the indicator) built into the OEM system to cover all of these possible scenarios and not have the darn thing read 3/4 at full and run dry at 1/5 tank indicated.
What all this means is one need not get all wrapped up in relatively high dollar parts to fix the non-problem of a gauge that is a few ohms off one side or both.
Pardon the lengthy diatribe, but this is a daily discussion we have working with our "street" customers. Enjoy!