Another fuel gauge thread

I'm in the process of replacing all my gauges. I chose autometer "old tyme" gauges just because I liked how they looked in the Scout. Seeing that the stock sender is 10-73 ohms, I bought a gauge that covers that range. I came to find out that the autometers are designed to work with Ford and chrysler non-linear sending units. They cover the same range, but read 25 ohms or so at half full, etc.

On another forum I was told that the IH sending units are linear, so it would seem to indicate that those senders will never work with anything but the IH gauges. Can anyone confirm? I see ihon has sending units for sale, are those be non-linear? I saw michael mentioned in another post that the ihon units are not identical to the factory units. How are they different? Thanks.

Typical aftermarket fuel gauges, no matter what "brand" are designed to power directly from switched b+.

The oem gauge systems used by ihc light line (and manufactured by stewart warner back in the day) are designed to power up from a 5vdc reference signal provided by the constant voltage regulator (cvr).

Aftermarket gauges use tank senders that can vary all over the place in their "matching" resistance characteristics/values.

Your "other forum" information is not at all correct, many other oem manufacturers used the same regulated power supply (5vdc) with the same resistive values for the sending units (namely Ford up through about 1979 when phased out). And,...ihc used various other systems as well on various vehicles over the ages.

This is simple...the sending unit resistive values have to match the gauge design selected. This has nothing to do with the operating voltage of the actual gauge itself.

Regarding the oem s80, the fuel gauge module is unique in that the cvr is actually a component inside the temperature gauge and hidden from view unless it's dissected. It's connected to the fuel module with a jumper.

We market the particular isspro line of fuel gauges (which are nominal 12vdc-powered involving no cvr) specifically because they can use the same sending units used in ihc-produced light line vehicles. On the other hand, we also have isspro gauges that can use other sending unit values as well.

The aftermarket autometer gauge is powered by b+, not a cvr/5vdc signal, and those must use the sending unit with a resistive value that is matched to the autometer gauge.

The light line fuel gauge senders we have in stock are either oem/nos or reproductions of the original ihc senders and work with the oem cvr system, though they can also be used with any aftermarket 12vdc gauge if the resistive value is proper.

This is a shot of the cvr inside a Scout 80 temperature gauge.

All that cvr stuff is history. I have completely rewired the vehicle and am not keeping any of that old nonsense. I've hooked up the fuel gauge according to its connection diagram, and that's not the issue. It is doing what it claims to do. Right now the sender is at 25 ohms, and the gauge reads half full. My question is just whether the IH sender is linear or Ford-like (non-linear). Autometer makes these gauges to retrofit older vehicles.

If the sender is linear, I'm screwed and need to replace the sender and probably the gauge as well (unless the ihon one is non-linear). If the IH sender is like Ford and chrysler, then I just need to fix up the connections to the tank.

I don't know what this "linear" shit is. I have Ford senders and I have ihc senders, the Ford senders are near identical to the sender used in the Scout 80/800 and the resistive values and actuation are identical, when the rheostats are tested in exactly the same positions.

I have also installed and used the autometer gauge with the oem s80/s800 sender (and the current repop version of the light line sender). The autometer gauge works perfectly as long as the sender float arm is adjusted for full travel.

A complete technical analysis of all gauge systems used by ihc for all models is found in every ihc service manual, the same section is simply reprinted over and over.

Here's what I'm talking about:

auto meter

mastiff said:

here's what I'm talking about:

auto meter

Click to expand...

So the movement of the guage itself, of the needle, is set to correspond differently throughout the resistance range. It sounds like you have the wrong guage and that linear movement allows for more accurate readings at the guage but in reality you need a guage that reads
full +/-10 ohms
half +/-25 ohms
empty +/-ohms

being that the needle movement or the elements reaction to the resistance of the sender is calibrated on that scale.

It's not the sender or the resistance value the sender has at level that is the problem but the guage itself.

Or as we say in the petro chem world you need a correctly calibrated instrument.

scoutpappa said:

so the movement of the guage itself, of the needle, is set to correspond differently throughout the resistance range. It sounds like you have the wrong guage and that linear movement allows for more accurate readings at the guage but in reality you need a guage that reads
full +/-10 ohms
half +/-25 ohms
empty +/-ohms

being that the needle movement or the elements reaction to the resistance of the sender is calibrated on that scale.

It's not the sender or the resistance value the sender has at level that is the problem but the guage itself.

Or as we say in the petro chem world you need a correctly calibrated instrument.

Click to expand...

Well, I need a gauge that matches the sender. It sounds like the sender is linear and the gauge is not. Problem is, I doubt anyone makes a gauge to match the factory sender. 10-73 gauges are made to match fords not scouts.

mastiff said:

well, I need a gauge that matches the sender. It sounds like the sender is linear and the gauge is not. Problem is, I doubt anyone makes a gauge to match the factory sender. 10-73 gauges are made to match fords not scouts.

Click to expand...

This is bullshit!

We have many threads right here in this sub-forum that state fact right from service manuals regarding the value of the oem sending units used in light line vehicles. Here is just a sample:

http://www.forums.IHPartsAmerica.com/electrical-tech/2326-ohm-readings-fuel-sender.html

Both Ford (through 1978) and ihc (and some other oem's) used the same pattern/value sender. I've already stated that in this thread! That sender value is not unique! The actual potentiometer used in the oem s80/s800 sender is identical in every respect to the same potentiometer used in the Ford products of the same era. The only difference is the mounting flange hole pattern, they do not interchange.

And...I've stated already that ihon does have isspro fuel gauges on the shelf that are used with the oem senders for Scout 80, Scout 800, Scout II and all pickalls, as well as some medium duty applications. And I stated that I personally have installed many of those using the oem senders (and gauges). Why would we market instruments that are not compatible with oem senders????

Here are the facts of the matter:

I have already purchased a full set of gauges that match, they are made by autometer. The fuel gauge is meant to work with a non-linear sender, meaning that when it's in the middle of its ohm range, it reads more like a quarter full than a half. I am being told that the IH sender is linear in its operation, so it would not match the autometer.

I suppose isspro May have a gauge to work on a linear 10-73 range, but I don't want to purchase a mismatched gauge to the rest of my set. It's also possible that I have been told the wrong thing by others and the IH gauges are non-linear the same as fords. I plan to pull my sender out and find out the truth as soon as I can.

michael mayben said:

this is bullshit!

We have many threads right here in this sub-forum that state fact right from service manuals regarding the value of the oem sending units used in light line vehicles. Here is just a sample:

http://www.forums.IHPartsAmerica.com/electrical-tech/2326-ohm-readings-fuel-sender.html

Both Ford (through 1978) and ihc (and some other oem's) used the same pattern/value sender. I've already stated that in this thread! That sender value is not unique! The actual potentiometer used in the oem s80/s800 sender is identical in every respect to the same potentiometer used in the Ford products of the same era. The only difference is the mounting flange hole pattern, they do not interchange.

And...I've stated already that ihon does have isspro fuel gauges on the shelf that are used with the oem senders for Scout 80, Scout 800, Scout II and all pickalls, as well as some medium duty applications. And I stated that I personally have installed many of those using the oem senders (and gauges). Why would we market instruments that are not compatible with oem senders????

Click to expand...

I knew that was coming . Just thought I would chime in and see the sparks fly :d

mastiff said:

here are the facts of the matter:

I have already purchased a full set of gauges that match, they are made by autometer. The fuel gauge is meant to work with a non-linear sender, meaning that when it's in the middle of its ohm range, it reads more like a quarter full than a half. I am being told that the IH sender is linear in its operation, so it would not match the autometer.

I suppose isspro May have a gauge to work on a linear 10-73 range, but I don't want to purchase a mismatched gauge to the rest of my set. It's also possible that I have been told the wrong thing by others and the IH gauges are non-linear the same as fords. I plan to pull my sender out and find out the truth as soon as I can.

Click to expand...

If you don't "like" the answers you receive for your questions here on this customer support forum, then you should reconsider your participation.

After testing and "measuring" more than 40 ihc-pattern (and quite a few Ford and chrysler pattern) fuel level senders, I think I know how to do it, I know how to diagnosis/troubleshoot 'em, and know what their resistive values are. And I know that those values are a somewhat greater tolerance range than +/- 10%!!!

And that includes testing many new current production light line senders on the shelf in order to see how they measure up regarding the "specification" for their resistive range.

You should have done your homework regarding what aftermarket gauges are compatible with which oem fuel gauge senders. Ihon offers aftermarket gauges which are compatible, it would be rather foolish to sell a gauge which is not compatible don't you think?

Are you certain that you purchased an autometer gauge for the 10>73 ohm sending unit? Their standard offering is for a sender value of 240>33 ohms which is plain old GM-based shit.

And once more,... I personally have installed an autometer fuel gauge (with a tank selector switching system) rated for the 10>73 sender in a Scout 80 with a custom wiring harness which I personally fabricated (not my own), using the original fuel tank senders which surprisingly were still functional. I did also install new floats on those senders as the originally floats had rotted away. We have new replacement floats for those senders on the shelf, they also fit several other ihc-produced vehicle fuel gauge systems.

I'm done with this thread.

Wow, sorry I annoyed you so much. I'm not certain what you think I'm disagreeing about. I really just wanted to know if the factory senders were like the old (non-linear) fords or unique IH items.

I certainly have a 10-73 gauge. I emptied one tank tonight and it reads 83 ohms right at the tank. I filled the other side to over full and it reads 15 at the switch. I haven't pulled the cover on that side yet so it could be a wiring or sender issue at this point. The gauge reads as expected with those ohm values.

If you made an autometer work with the stock sender, that's a good data point. Every autometer 10-73 gauge I looked at on summit (I looked at a bunch today) had the non-linear markings on the face, so I suspect all they are all that way. This would tell me that the Scout senders are like non-linear fords.

I won't bug you anymore.

michael mayben said:

the oem gauge systems used by ihc light line (and manufactured by stewart warner back in the day) are designed to power up from a 5vdc reference signal provided by the constant voltage regulator (cvr)..........

Many other oem manufacturers used the same regulated power supply (5vdc) with the same resistive values for the sending units (namely Ford up through about 1979 when phased out). And,...ihc used various other systems as well on various vehicles over the ages.....

Regarding the oem s80, the fuel gauge module is unique in that the cvr is actually a component inside the temperature gauge and hidden from view unless it's dissected. It's connected to the fuel module with a jumper.....

Click to expand...

Hi michael, don't mean to totally hijack this thread, but it pertains to a thread I just started yesterday and pretty much solves my query....

http://www.forums.IHPartsAmerica.com/electrical-tech/7142-Scout-80-fuel-gauge-voltage-ohms.html

In doing a bunch more searching here and on other binder forums I realized that the voltage feeding the oe gages on the model 80 is, or should be 5vdc. This is a very big deal and was the problem with my gauges over-reading.

After figuring this out I went to radioshack and bought a 5vdc "voltage regulator" for $1.29. It looked like a small computer chip and had a max input rating of 35 volts. I soldered the appropriate wires to the three leads of the regulator/reducer as per the diagram on the package - input, ground & output - hooked it all up and shazam!!! It worked!!!! The gages read correctly.... = )≈ the only problem was the regulator unit was pretty delicate and I broke it while installing it permanently so I need to go back down to rs this morning and repeat the process.

Looking at the inside of the gage you have pictured above, im just wondering if I shouldn't just open up the whole gage and remove the old resistor and install the new one?

Thanks for all your info on this thread!