Auto meter fuel gauge reading wrong....

[rtreads]

Ok, so its been a year and I'm tired of having a fuel gauge that only I know how to read. I am having trouble getting my fuel sender calibrated. I have an autometer fuel gauge that has an adjustable pot on back to help calibrate fuel senders. With mine, if I adjust it all the way out, the needle goes way down on full. If it adjust it all the way in, the needle only goes to 3/4 at full. In addition to being off by 1/4 tank at full, it has a funny scale too. At half full, the gauge reads 1/4 full. So burning the first half tank shows a half tank of movment on the guage; from 3/4 down to 1/4. Now the second half of tank is shown only in the last 1/4 of the gauge and empty on the gauge is empty in the tank. Does this make sense?

Also I have a BC EFI tank, with the pump in the tank and their fuel sender. How can I make this accutate? Can I just add a second pot type resistor to make it work?

THANKS FOR ALL THE HELP!!

 

[70_Steve]

I have an autometer fuel gauge that has an adjustable pot on back to help calibrate fuel senders.

Waht is the model number of the Autometer gauge?

The stock (and BCBs) sender is 73 to 10 ohms. 73 ohms empty to 10 ohms full.

 

[rtreads]

Waht is the model number of the Autometer gauge?

The stock (and BCBs) sender is 73 to 10 ohms. 73 ohms empty to 10 ohms full.

I dont know the model number. The PO installed it?

 

[rtreads]

I think the gauge is the heritage series...

I know what the ohms are the for sender. What I need is a solution to make the spketrum adjustable to make the gauge read right. I hope that makes sense.

 

[Viperwolf1]

Senders have a certain function curve between the input (fuel level) and the output (resistance). This curve is counteracted at the gauge to provide a gauge reading that is more linear. The autometer gauge has a signal conditioner (variable resistor) at the input to adjust scale. This scale adjustment may not be working ideally with the range of the Ford style sender. Something you could try is to put a resistor in-line with the sender wire then adjust the gauge. What this may do is change the shape of the gauge curve to provide a more linear output. I'd try a 20 or 30 ohm resistor (1/2 watt) and see how that works.

There could also be a problem with the tank sender and it's range of motion but that requires a lot more work. Try the easy stuff first.

 

[rtreads]

Senders have a certain function curve between the input (fuel level) and the output (resistance). This curve is counteracted at the gauge to provide a gauge reading that is more linear. The autometer gauge has a signal conditioner (variable resistor) at the input to adjust scale. This scale adjustment may not be working ideally with the range of the Ford style sender. Something you could try is to put a resistor in-line with the sender wire then adjust the gauge. What this may do is change the shape of the gauge curve to provide a more linear output. I'd try a 20 or 30 ohm resistor (1/2 watt) and see how that works.

There could also be a problem with the tank sender and it's range of motion but that requires a lot more work. Try the easy stuff first.

YES. EASY FIRST!.

Thanks for the idea! This is what I was thinking of, but I didn't know how it would work. Where can I put it in that wire? The easiest place in along the frame rail. Is this tolerable, or does it need to be in the cab? And I would just cut the wire and install this resistor?

thanks phil!

 

[broncnaz]

Not sure on what type of sender that BC uses on there tanks but 23 gallon tanks are a little tough to get the fuel level reading correctly. Usually have to adjust the float arm to get it to read correctly.
But I usually check the sender against the tank and the guage for accuracy. which means you need to pull the sender.
In your case this may be your best bet so you can check the sending unit against the gauge and get themn reading correctly then if need be adjust the float compared to the tank so the fuel level reads like you want it. But as I said I dont know what type of sender BC uses and you might not even be able to do that,

To me adding a resistor just throws the whole thing out of wack as adding more resistance would cause the gauge to read even lower. Wouldnt it? as adding 20-30 ohms resistance at full tank will put you off by 30-40 ohms when you need 10 ohms to read full. I could be wrong I'm no electrical engineer.
But I'm betting on the sending unit needs to be adjusted. Or you just have the wrong guage for the sending unit you have.

 

[70_Steve]

And I would just cut the wire and install this resistor?

I dunno if I'd cut anything just yet. If you've got the stock sender, there's a wiring plug on it. One side goes to ground, the other to the gauge. remove the connector and connect the resistor between one side of the sender and the side of the connector that goes back up to the gauge. Connect the other side of the sender to ground. Then see what you've got. Might take a couple aligator clip jumpers to do that, but better than cutting wires at this point.

 

[Viperwolf1]

To me adding a resistor just throws the whole thing out of wack as adding more resistance would cause the gauge to read even lower. Wouldnt it? as adding 20-30 ohms resistance at full tank will put you off by 30-40 ohms when you need 10 ohms to read full. I could be wrong I'm no electrical engineer.
But I'm betting on the sending unit needs to be adjusted. Or you just have the wrong guage for the sending unit you have.

The key here is the adjustable gauge. You wouldn't be able to do this with the stock gauge for the reasons you mention. The autometer gauge is design to accept a variety of sender ranges.

 

[Viperwolf1]

YES. EASY FIRST!.

Thanks for the idea! This is what I was thinking of, but I didn't know how it would work. Where can I put it in that wire? The easiest place in along the frame rail. Is this tolerable, or does it need to be in the cab? And I would just cut the wire and install this resistor?

thanks phil!

Put it on the end of the wire. You probably can't get to the sender end so use the gauge end. One side of the resistor to the sender wire and the other side to the gauge "S" terminal.

 

[msweb]

Senders have a certain function curve between the input (fuel level) and the output (resistance). This curve is counteracted at the gauge to provide a gauge reading that is more linear. The autometer gauge has a signal conditioner (variable resistor) at the input to adjust scale. This scale adjustment may not be working ideally with the range of the Ford style sender. Something you could try is to put a resistor in-line with the sender wire then adjust the gauge. What this may do is change the shape of the gauge curve to provide a more linear output. I'd try a 20 or 30 ohm resistor (1/2 watt) and see how that works.

There could also be a problem with the tank sender and it's range of motion but that requires a lot more work. Try the easy stuff first.

It is MHO that only YOU could have said that in a language that it actually makes sense to me. I bow down to your tingling electrical senses!

OBTW - this isn't a hijack - I just ordered a Autometer fuel level gauge - # 3515. I doubt it has the calibration feature but I'll be following this thread closely!

 

[broncnaz]

Well I hope it works. But I think the adjustable gauge thing is kinda like the stock guage it allows for minor adjustment due to minor varibles in sending units.
A few of the guages I just looked up were universal but they had presets so maybe thats what he has and instead of turning the pot all the way in or out maybe its a in between setting.

 

[rtreads]

I REALLY appreciate all of your input. I would pull the tank and mess with the sender, however I dont feel thats the problem. The sender float goes from "full" stop to "empty" stop without any thing limiting its travel. The issue isn't that the float isnt moving all the way. The issue is that the gauge doesn't read the senders "full" as full. Rather, it translates the "full" of the sender as 3/4. Therefore I feel that there needs to be some sort of external resistor to help the translation come across clearly. Hope this isn't confusing...

Viper, Can I use an adjustable resistor (pot) to do what you suggest? This way I can get it just right? I feel that if the gauge has an adjustable readout and the external resistor that I add can be adjusted, I should be able to get it right? I know this MIGHT not fix the fact that the spketrum of the readout isnt consistant to whats in the tank, but at least full will be full... right?

 

[Viperwolf1]

You could use an adjustable pot but they're hard to find with that small a range and wattage. Plus you have adjustment at the gauge already. You can go to any Radio Shack and pick up a resistor for $1.

 

[DonsBolt]

A lot of us are having issues with the sending unit on these new bigger tanks. So here is a option for those who run aftermarket gauges.

get this sender, and the gauge that matches this sending unit. In your case being a adjustable gauge I am sure this sending unit will work with yours

http://www.autometer.com/tech_faq_answer.aspx?sid=1&qid=38

 

[rtreads]

A lot of us are having issues with the sending unit on these new bigger tanks. So here is a option for those who run aftermarket gauges.

get this sender, and the gauge that matches this sending unit. In your case being a adjustable gauge I am sure this sending unit will work with yours

http://www.autometer.com/tech_faq_answer.aspx?sid=1&qid=38

I tried your link. It doesnt pull up a sender?

 

[scsm76]

I have issues with the BC tank sender as well. The problem is the Ford sending units are non-linear the sending unit used in the BC tanks are linear. So the guge is correct at full and empty but off any where in between.
Here is Auto meters explanation of the problem and there suggestion to fix it, basically buying a new sender and guage. I wish there was a better cheaper solution.

 

[broncnaz]

I REALLY appreciate all of your input. I would pull the tank and mess with the sender, however I dont feel thats the problem. The sender float goes from "full" stop to "empty" stop without any thing limiting its travel. The issue isn't that the float isnt moving all the way. The issue is that the gauge doesn't read the senders "full" as full. Rather, it translates the "full" of the sender as 3/4. Therefore I feel that there needs to be some sort of external resistor to help the translation come across clearly. Hope this isn't confusing...

Right the sending unit has a range of travel that is not impeeded but is the sending units float actually in the right position in relationship to the amount of gas in the tank. If your reading 3/4 tank and get no movement until 1/2 the tank is used then it goes to 1/4 tank that tells me the float is probably to low in relationship to the gas in the tank.
I just dont see the resistor working if you have a gauge that is not for your sending unit. I imagine that BC uses a sending unit with stock ford ohms ranges. If your guage is not for the ford range you'll never get it there with resistors hech the gm range is exactly opposite of the ford range ie more ohms at full than empty vs less ohms at full than empty. See chart.



Most GM vehicles 1965 to present full 90 empty 0
Most Ford & Chrysler vehicles full 10 empty 73
3262 fuel level sender full 33 empty 240
Most GM vehicles before 1965 full 30 empty 0
Most Ford vehicles '87 to present full 158 empty 16
Adding more ohms to any of these just wont work

 

[rekoj71]

I went with an aftermarket gauge and it came with a matching sender for that guage. It was also very easy to fit it to my BC's tank. aftermarket senders are designed with a height adjustment and an arm/range of travel adjustment and the pieces are all pretty close to the same. I used the BC braketry but removed and replaced the electrical parts with the ones that came with my gauge and my gauge works perfectly. I had a hard time finding a gauge that used the older Ford sender so it was easier for me to replace the sender to the right one for the gauges I wanted. You might want to try getting a (heaven forbid) GM style sender or whatever autometer recomends for that gauge as that may work better with your aftermarket gauge, although I will admit I'm not familiar with an adjustable gauge like you seem to be talking about.

 

[msweb]

I think I may switch over to a cork with a string tied to it, the other end tied to the needle on my gauge......