Autometer fuel level gauge (#4315) ohms

[zlat347ci]

hi all,

Anyone using the 4315 autometer fuel level gauge, any issues?

everything is brand new, from fuel sender to gauge to wiring. earth strap to sender aswel.

without the sender wire connected to fuel gauge, readings at fuel sender directly and upfront show 75ohms empty and 8 ohms on full with multi meter which is correct

with sender wire connected to gauge, exact same test as above, empty changes to 30ohms and full is 8 ohms?

the minute the sender wire is connected it drops the ohms and gauge reads incorrectly.

so i bought another brand new gauge, and bench tested it all, eliminated the possibility of bad grounds ect, and same result..... also tested another sender, ran out of ideas, any thoughts?

video of issue:
https://youtu.be/RMbX38vq12w


 

[MStang67]

Hi,

Is the gauge not suppose to be connected in the dashboard via a kind of relay to get current intermitently and not directly to your power supply?

Should try connecting gauge in the dashboard then to the sender unit.

rgds

[jbb]

may seem like a silly question to you , but what does the actual gauge show when you move the sender from the two extremes??
You haven't told us what the gauge is actually doing in relation to your ohm readings.

And , no it doesnt matter that your putting power on to it direct when testing, as long as you have it through fuse.


Jbb

[zlat347ci]

Hi,

Is the gauge not suppose to be connected in the dashboard via a kind of relay to get current intermitently and not directly to your power supply?

Should try connecting gauge in the dashboard then to the sender unit.

rgds

Already tried this and thr same result incar or bench testing

[zlat347ci]

may seem like a silly question to you , but what does the actual gauge show when you move the sender from the two extremes??
You haven't told us what the gauge is actually doing in relation to your ohm readings.

And , no it doesnt matter that your putting power on to it direct when testing, as long as you have it through fuse.


Jbb

So with 20ltrs of fuel with the sender wire disconnected from gauge i read 55ohms, when u connect the sender wire to gauge it shows 24 ohms.

The gauge climbs just over the the E marker. Now if 10ohms is full 24 ohms shohld be 3/4 of tank on gauge?

I remember reading somewhere about a resistor being placed inbetween the sender wire ans grouns on gauge.

[MStang67]

There must be a problem with the gauge then which is acting like there is a resistor in parallel and reducing the total resistance...Are the connection ok on the gauge?
If the gauge range is 75 - 10 ohms than the 55 ohms for 20 litres seems about right.

[zlat347ci]

All connection are perfect, crimped on.

Just thought, what are the chamces of 2 gauges being bad.amd javing the same issue. First gauge is 2 years old, other gauge is brand new.

I stumbled accross the below somebloke additing a resistor between sender/ground connection, may be worth a try

https://www.stangnet.com/mustang-forums/threads/autometer-instrument-gauge-conversion.795875/

[MStang67]

All connection are perfect, crimped on.

Just thought, what are the chamces of 2 gauges being bad.amd javing the same issue. First gauge is 2 years old, other gauge is brand new.

I stumbled accross the below somebloke additing a resistor between sender/ground connection, may be worth a try

https://www.stangnet.com/mustang-forums/threads/autometer-instrument-gauge-conversion.795875/

That link has the answer in it :  The Autometer 4315 has  a Non Linear movement to work with a stock Ford sending unit ( which would have the same non linear movement.
Aftermarket sending units like the Scottdrake have a linear movement which is making the gauge reading unaccurately.

With your sending unit not wired you get 75 ohms, when wired 30 ohms, you gauge empty is 73 ohms.  I would put a 1/2w 43 ohms resistor on sending wire ....however need to check the reading with full tank!

I am going to do some testing on my side as well now!  I have a spare sending unit to play with!!

[zlat347ci]

Yes thats right.
I put a 47ohm 1/2 watt resister between sender wire and ground. It changed the 30 ohms on empty to 21 ohm.
With the sender at empty level and resister connected the gauge starts at quarter tank on empty.

Autometer make the same gauge for.linear sender. 4319 model. Third time lucky hopefully.

So.many people use aftermarket senders, thought this would have been a wider issue.

[MStang67]

I checked my  actual reading:

I dont know how much fuel I have in my tank but I measured 14.2 Ohms at the sending unit and my gauge needle is just above 1/2 tank ......

[zlat347ci]

I checked my  actual reading:

I dont know how much fuel I have in my tank but I measured 14.2 Ohms at the sending unit and my gauge needle is just above 1/2 tank ......

14.2 Ohms would ideally need to be in between 3/4 to full tank.

played with some resistors to try and correct it however still inaccurate.

ive ordered the linear version of the gauge now, so once it arrives will come back with some new results.   

[MStang67]

Well,

After playing with a potentiometer to check the needle movement with various resistance, I got to think that in anycase , the reading you get when wiring the sending unit is not really relevant  - only the sending unit resistance reading without wiring is important.

Resistance            Resistance reading
set on                   wired to gauge             Gauge Needle position
potentiometer

75 ohms               27 Ohms                      Just before the E thick dash
63.1 ohms            26.4 Ohms                   On the E thick dash
52 ohms               24.5 ohms                    Just pass the E thick dash
43 Ohms              22.4 ohms                     Touching the thin dash
30 Ohms              18.4 ohms                    1/4 tank
26.2 Ohms            17 ohms                       between 1/4 & 1/2 tank

then my potentiometer started malfunctioning!!

I connected a resistance of 15 ohms to check and the needle went to a little more than 3/4 full tank.


S0 the stock gauge works as it should ( 75 ohms empty - 9 ohms full)  with the resistance range on which the sending unit is meant to work .  Next step now, as my sending unit is already in my tank is to know the amount of fuel required for each of the above readings! Will drain the fuel tank and monitor progress of needle / ohms step by step ( for every gallon ).

[zlat347ci]

Well,

After playing with a potentiometer to check the needle movement with various resistance, I got to think that in anycase , the reading you get when wiring the sending unit is not really relevant  - only the sending unit resistance reading without wiring is important.

Resistance            Resistance reading
set on                   wired to gauge             Gauge Needle position
potentiometer

75 ohms               27 Ohms                      Just before the E thick dash
63.1 ohms            26.4 Ohms                   On the E thick dash
52 ohms               24.5 ohms                    Just pass the E thick dash
43 Ohms              22.4 ohms                     Touching the thin dash
30 Ohms              18.4 ohms                    1/4 tank
26.2 Ohms            17 ohms                       between 1/4 & 1/2 tank

then my potentiometer started malfunctioning!!

I connected a resistance of 15 ohms to check and the needle went to a little more than 3/4 full tank.


S0 the stock gauge works as it should ( 75 ohms empty - 9 ohms full)  with the resistance range on which the sending unit is meant to work .  Next step now, as my sending unit is already in my tank is to know the amount of fuel required for each of the above readings! Will drain the fuel tank and monitor progress of needle / ohms step by step ( for every gallon ).



Good work mate! thanks.

My fuel sender reads perfectly against multi meter reading without it being connected to the gauge, its only when the gauge is in circuit that distorts the numbers, then projects the wrong reading. The standard gauge may be calibrated that way to read the lower ohms? not sure, where as the aftermarket gauge may rely on the raw number?